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#include <bits/stdc++.h>
using namespace std;
const int maxn = 1000 + 10;
long long c[maxn][maxn], f[10] = {1, 0, 1, 2, 9}, ans;
int main() {
long long n, k;
cin >> n >> k;
for (int i = 1; i <= n; i++) {
c[0][i] = 1;
c[i][0] = 1;
c[i][i] = 1;
}
for (int i = 1; i <= n; i++)
for (int j = 0; j <= n; j++)
if (i <= j) c[i][j] = c[i][j - 1] + c[i - 1][j - 1];
for (int i = 0; i <= k; i++) ans += (c[i][n] * f[i]);
cout << ans << endl;
return 0;
}
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#include <bits/stdc++.h>
using namespace std;
const int MAX = 1e3 + 5;
long long int Table[MAX][MAX];
int Dearrangement(int n) {
if (n == 0) return 1;
if (n == 1) return 0;
if (n == 2) return 1;
int ans = (n)*Dearrangement(n - 1) + ((n % 2) ? -1 : 1);
return ans;
}
long long int ncr(int n, int r) {
if (r == 0 || n == r) return Table[n][r] = 1;
if (n < 1 || r < 1) return 0;
if (Table[n][r] != -1) return Table[n][r];
return Table[n][r] = ncr(n - 1, r - 1) + ncr(n - 1, r);
}
int main() {
memset(Table, -1, sizeof Table);
int n, k;
cin >> n >> k;
for (int i = 0; i <= n; i++) Table[n][i] = ncr(n, i);
long long int ans = 0;
for (int i = 0; i <= k; i++) {
ans += Table[n][n - i] * 1LL * Dearrangement(i);
}
cout << ans;
return 0;
}
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#include <bits/stdc++.h>
using namespace std;
long long N, K;
int main() {
ios_base::sync_with_stdio(0);
cin >> N >> K;
long long ans = 0;
ans++;
ans += N * (N - 1) / 2;
if (K == 1) {
cout << "1" << endl;
return 0;
}
if (K == 2) {
cout << ans << endl;
return 0;
}
ans += N * (N - 1) * (N - 2) / 3;
if (K == 3) {
cout << ans << endl;
return 0;
}
ans += N * (N - 1) * (N - 2) * (N - 3) * 9 / 24;
if (K == 4) {
cout << ans << endl;
return 0;
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long dearrange[5] = {1, 0, 1, 2, 9}, ans, n, k;
long long nCr(int N, int R) {
long long num = 1, den = 1;
for (int i = 2; i <= N - R; ++i) den *= i;
for (int i = R + 1; i <= N; ++i) num *= i;
return num / den;
}
int main() {
cin >> n >> k;
for (int i = n - k; i <= n; ++i) ans += nCr(n, i) * dearrange[n - i];
cout << ans;
}
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#include <bits/stdc++.h>
using namespace std;
int main() {
int a[5];
for (int i = 1; i <= 4; i++) a[i] = i;
int ans = 0;
do {
int cnt = 0;
for (int i = 1; i <= 4; i++) {
if (a[i] != i) cnt++;
}
if (cnt == 4) ans++;
} while (next_permutation(a + 1, a + 5));
int n, k;
scanf("%d%d", &n, &k);
if (k == 1)
printf("1\n");
else if (k == 2) {
int ans = n * (n - 1) / 2 + 1;
printf("%d\n", ans);
} else if (k == 3) {
int ans = n * (n - 1) * (n - 2) / 3 + n * (n - 1) / 2 + 1;
printf("%d\n", ans);
} else {
long long int ans = 9LL * n * (n - 1) * (n - 2) * (n - 3) / 24 +
n * (n - 1) * (n - 2) / 3 + n * (n - 1) / 2 + 1;
printf("%lld\n", ans);
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int power(long long int x, long long int y) {
long long int temp;
if (y == 0) return 1;
temp = power(x, y / 2);
if (y % 2 == 0)
return temp * temp;
else
return x * temp * temp;
}
bool prime_check(long long int n) {
long long int i, j;
if (n == 1) {
return false;
}
for (i = 2; i <= sqrt(n); i++) {
if (n % i == 0) {
return false;
}
}
return true;
}
long long int fact(long long int n) {
long long int prod = 1;
for (long long int i = 1; i <= n; i++) {
prod = (prod * i);
}
return prod;
}
bool vowl(char c) {
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}
long long int ncr(long long int x, long long int y) {
long long int ans = 1;
for (long long int i = 1; i <= y; i++) {
ans = ans * x;
x--;
}
ans = ans / fact(y);
return ans;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
long long int n, k;
cin >> n >> k;
long long int ans = 0;
if (k == 4) {
ans += ncr(n, 4) * 9;
}
if (k >= 3) ans += ncr(n, 3) * 2;
if (k >= 2) ans += ncr(n, 2);
if (k >= 1) ans++;
cout << ans << "\n";
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int dp[(int)(1e3 + 5)], n, k, ans = 1,
com[(int)(1e3 + 5)][(int)(1e3 + 5)];
long long int dfs(int n) {
if (n == 1) return 0;
if (n == 2) return 1;
if (~dp[n]) return dp[n];
return dp[n] = ((n - 1) * (dfs(n - 1) + dfs(n - 2)) % (1000000007)) %
(1000000007);
}
int main() {
memset(dp, -1, sizeof(dp));
scanf("%lld %lld", &n, &k);
com[0][0] = 1;
for (int i = 1; i <= n; i++) {
com[i][0] = 1;
for (int j = 1; j <= i; j++) com[i][j] = com[i - 1][j] + com[i - 1][j - 1];
}
for (int i = k; i > 1; i--) ans += dfs(i) * com[n][i];
printf("%lld\n", ans);
}
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#include <bits/stdc++.h>
using namespace std;
vector<int> adj[100005], vec;
bool vis[100005];
long long lawda_mera[100005];
void barood_bharo() {
for (int i = 3; i < 100005; i++) {
lawda_mera[i] = i * lawda_mera[i - 1] + (long long)pow(-1, i);
}
}
long long kun_faya(long long a, long long b) {
long long res = 1;
for (int i = 0; i < b; i++) res *= (a - i);
return res;
}
long long fact(long long n) {
if (n == 1) return 1;
return n * fact(n - 1);
}
int main() {
lawda_mera[1] = 1;
lawda_mera[2] = 1;
barood_bharo();
long long n, k;
cin >> n >> k;
long long ans = 1;
for (int i = 2; i <= k; i++) {
ans += (kun_faya(n, i) / fact(i)) * lawda_mera[i];
}
cout << ans << "\n";
}
|
#include <bits/stdc++.h>
using namespace std;
void print(long long ans) {
cout << ans << "\n";
exit(0);
}
int main() {
long long n, k;
cin >> n >> k;
k = min(k, n);
long long ans = 1;
if (k == 1) {
print(ans);
}
if (k >= 2) {
ans += n * (n - 1) / 2;
}
if (k >= 3) {
ans += 2 * n * (n - 1) * (n - 2) / 6;
}
if (k >= 4) {
ans += 9 * n * (n - 1) * (n - 2) * (n - 3) / 24;
}
print(ans);
}
|
#include <bits/stdc++.h>
using namespace std;
const long double PI = (long double)(3.1415926535897932384626433832795);
int parity_check(int n) {
int par = n;
par = par ^ (par >> 1);
par = par ^ (par >> 2);
par = par ^ (par >> 4);
par = par ^ (par >> 8);
par = par ^ (par >> 16);
if (par % 2 == 1) {
return 1;
} else {
return 0;
}
}
int lcs(string X, string Y, int m, int n) {
int L[m + 1][n + 1];
int i, j;
for (i = 0; i <= m; i++) {
for (j = 0; j <= n; j++) {
if (i == 0 || j == 0)
L[i][j] = 0;
else if (X[i - 1] == Y[j - 1])
L[i][j] = L[i - 1][j - 1] + 1;
else
L[i][j] = max(L[i - 1][j], L[i][j - 1]);
}
}
return L[m][n];
}
int long long gcd(int long long a, int long long b) {
if (a == 0) {
return b;
}
return gcd(b % a, a);
}
int long long lcm(int long long a, int long long b) {
int long long pro = a * b;
int long long ans = gcd(a, b);
pro = pro / ans;
return pro;
}
int long long fast_power(int long long a, int long long b, int long long p) {
if (b == 0) {
return (1 % p);
}
int long long t = fast_power(a, b / 2, p);
int long long ans = (t * t) % p;
if (b % 2) {
ans = (ans * (a % p)) % p;
}
return ans;
}
bool prime_check(int long long n) {
int long long i, j;
if (n == 1) {
return false;
}
for (i = 2; i <= sqrt(n); i++) {
if (n % i == 0) {
return false;
}
}
return true;
}
int long long fact(int long long n, int long long mod) {
int long long prod = 1;
for (int long long i = 1; i <= n; i++) {
prod = (prod * i) % mod;
}
return prod;
}
int long long fac[500001];
void calc_fac() {
fac[0] = 1;
for (int i = 1; i <= 15; i++) {
fac[i] = (fac[i - 1] * i);
}
}
int long long comb(int long long n, int long long r, int long long mod) {
if (r > n) {
return 0;
}
int long long ans = fac[n];
int long long den = (fac[n - r] * fac[r]) % mod;
ans = (ans * fast_power(den, mod - 2, mod)) % mod;
return ans;
}
const int M = (int)(2e6 + 239);
int pref[M], c;
string solve_palindrome(const string& s) {
string a = s;
reverse(a.begin(), a.end());
a = s + "#" + a;
c = 0;
for (int i = 1; i < (int)a.size(); i++) {
while (c != 0 && a[c] != a[i]) c = pref[c - 1];
if (a[c] == a[i]) c++;
pref[i] = c;
}
return s.substr(0, c);
}
void mera_sieve() {
bool prime[6000013];
memset(prime, true, sizeof(prime));
for (int long long p = 2; p * p <= 6000012; p++) {
if (prime[p] == true) {
for (int long long i = p * p; i <= 6000012; i += p) prime[i] = false;
}
}
for (int long long i = 2; i <= 6000012; i++) {
if (prime[i]) {
}
}
}
int long long com(int long long n, int long long r) {
int long long ans = 1;
for (int long long i = n - r + 1; i <= n; i++) {
ans *= i;
}
for (int long long i = 1; i <= r; i++) {
ans /= i;
}
return ans;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
;
int long long n, k, i, j;
calc_fac();
int long long test = 1;
while (test--) {
cin >> n >> k;
int long long ans = 0;
for (i = k; i > 0; i--) {
if (i == 4) {
ans += (com(n, i) * 9);
}
if (i == 3) {
ans += (com(n, i) * 2);
}
if (i == 2) {
ans += (com(n, i));
}
if (i == 1) {
ans += 1;
}
}
cout << ans << "\n";
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long C(int n, int k) {
long long temp = 1;
if (k < n / 2) {
for (int i = 0; i < k; i++) temp *= n - i;
for (int i = 1; i <= k; i++) temp /= i;
} else {
for (int i = n - k; i > 0; i--) temp *= n - i + 1;
for (int i = n - k; i > 0; i--) temp /= i;
}
return temp;
}
int main() {
int n, k;
long long ans;
cin >> n >> k;
if (k == 1) cout << 1 << endl;
if (k == 2) {
ans = 1 + C(n, 2);
cout << ans << endl;
}
if (k == 3) {
ans = 1 + C(n, 2) + 2 * C(n, 3);
cout << ans << endl;
}
if (k == 4) {
ans = 1 + C(n, 2) + 2 * C(n, 3) + 9 * C(n, 4);
cout << ans << endl;
}
}
|
#include <bits/stdc++.h>
using namespace std;
const long long N = 31;
long long timer, cc, cc1;
void boost() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
}
long long ncr[1005][5];
void compute() {
long long i, j;
for (i = 0; i < 1005; i++) {
for (j = 0; j < 5; j++) {
if (j == 0 || i == j) {
ncr[i][j] = 1;
} else if (j > i) {
ncr[i][j] = 0;
} else
ncr[i][j] = ncr[i - 1][j - 1] + ncr[i - 1][j];
}
}
}
int main() {
boost();
compute();
long long i, t, n, q, l, r, ans, mid, c = 0, j, k, z, tc;
long long h, m, u, mm, w, mx, x, y, l1, r1, d = 0, mask;
long double f, f1;
long long a[5];
a[0] = 0;
a[1] = 0;
a[2] = 1;
for (i = 3; i < 5; i++) {
a[i] = (i - 1) * (a[i - 1] + a[i - 2]);
}
cin >> n >> k;
ans = 1;
for (i = 0; i <= k; i++) {
z = ncr[n][i] * a[i];
ans += z;
}
cout << ans << '\n';
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long n, k;
cin >> n >> k;
long long c = 0;
if (k >= 1) c++;
if (k >= 2) {
c = c + (n * (n - 1)) / 2;
}
if (k >= 3) {
for (long long i = 2; i < n; i++) {
c = c + (i * (i - 1));
}
}
if (k >= 4) {
for (long long j = 3; j < n; j++) {
for (long long i = 2; i < j; i++) {
c = c + (j * (j - 1)) / 2 * 3;
}
}
}
cout << c;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int c(int n, int r) {
if (r == n || r == 0)
return 1;
else if (r == 1 || r == n - 1)
return n;
else
return c(n - 1, r - 1) + c(n - 1, r);
}
long long int d(int n) {
if (n == 0 || n == 2) return 1;
if (n == 1) return 0;
return (n - 1) * (d(n - 1) + d(n - 2));
}
int main() {
int n, k;
cin >> n >> k;
long long int ans = 0;
for (int i = 0; i <= k; i++) {
ans += c(n, i) * d(i);
}
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
int main() {
std::ios_base::sync_with_stdio(false);
std::cout.tie(nullptr);
std::cin.tie(nullptr);
std::cerr.tie(nullptr);
int64_t n, k;
std::cin >> n >> k;
if (k == 1) std::cout << "1\n";
if (k == 2) {
int64_t res = (n * (n - 1)) / 2 + 1;
std::cout << res << '\n';
}
if (k == 3) {
int64_t res = (n * (n - 1) * (n - 2)) / 3 + (n * (n - 1)) / 2 + 1;
std::cout << res << '\n';
}
if (k == 4) {
int64_t res = (n * (n - 1) * (n - 2)) / 3 + (n * (n - 1)) / 2 +
9 * (n * (n - 1) * (n - 2) * (n - 3)) / 24 + 1;
std::cout << res << '\n';
}
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long n, k;
cin >> n >> k;
long long end = 1 + (k >= 2) * (n * (n - 1) / 2) * 1 +
(k >= 3) * (n * (n - 1) * (n - 2) / 6) * 2 +
(k >= 4) * (n * (n - 1) * (n - 2) * (n - 3) / 24) * 9;
cout << end;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e4 + 5;
using LL = unsigned long long;
LL ans[maxn][5];
const int INF = 0x3f3f3f3f;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
for (LL i = 4; i <= 1000; i++) {
ans[i][1] = 1;
ans[i][2] = ans[i][1] + i * (i - 1) / 2;
ans[i][3] = ans[i][2] + i * (i - 1) * (i - 2) / 3;
ans[i][4] = ans[i][3] + i * (i - 1) * (i - 2) * (i - 3) / 8 * 3;
}
int n, k;
cin >> n >> k;
cout << ans[n][k] << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int MAX_N = 1000 + 20;
long long int dp[5];
void make_dp() {
dp[0] = 1;
dp[2] = 1;
int sum = 1;
for (int i = 3; i <= 4; ++i) {
dp[i] = (i - 1) * sum;
sum += dp[i];
}
}
static inline long long int get(int n, int k) {
long long int devision = 1, number = 1;
for (int i = 1; i <= k; ++i) {
devision *= i;
number *= (n - i + 1);
}
return number / devision;
}
int main() {
int n, k;
cin >> n >> k;
long long int answer = 0;
make_dp();
for (int i = 0; i <= k; ++i) {
answer += dp[i] * get(n, i);
}
cout << answer << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int n, k;
long long get(int x) {
long long ans = 1;
for (int i = 0; i < x; i++) {
ans *= (n - i);
}
for (int i = x; i > 1; i--) ans /= i;
return ans;
}
int main() {
scanf("%d%d", &n, &k);
long long ans = 1;
int a[5] = {0, 0, 1, 2, 9};
for (int i = 2; i <= k; i++) {
ans += get(i) * a[i];
}
printf("%lld\n", ans);
}
|
#include <bits/stdc++.h>
using namespace std;
long long n;
long long k, m;
int main() {
cin >> n >> k;
long long sum = 1;
vector<long long> c(5, 0), p(5, 0);
p[2] = 1;
p[3] = 2;
p[4] = 9;
c[2] = n * (n - 1) / 2;
c[3] = n * (n - 1) * (n - 2) / 6;
c[4] = n * (n - 1) * (n - 2) * (n - 3) / 24;
for (int i = 2; i <= k; i++) {
sum += c[i] * p[i];
}
return cout << sum, 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long f(long long x, long long y) {
long long h = 1;
long long g = 1;
for (long long i = x; i > x - y; i--) h *= i;
for (long long i = y; i >= 1; i--) g *= i;
return h / g;
}
signed main() {
long long n, k;
cin >> n >> k;
if (k == 4) {
cout << f(n, 4) * 9 + f(n, 3) * 2 + f(n, 2) + 1;
return 0;
}
if (k == 3) {
cout << f(n, 3) * 2 + f(n, 2) + 1;
return 0;
}
if (k == 2) {
cout << f(n, 2) + 1 << endl;
return 0;
}
cout << 1 << endl;
}
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#include <bits/stdc++.h>
using namespace std;
int fact(int n) {
if (n == 1 || n == 0) return 1;
return fact(n - 1) * n;
}
int main() {
long long n, r, a, b, c;
cin >> n >> r;
a = 2;
b = 6;
c = 24;
if (r == 1) {
cout << 1;
return 0;
}
if (r == 2) {
cout << (n * (n - 1) / a) + 1;
return 0;
}
if (r == 3) {
cout << (n * (n - 1) * (n - 2)) / b * 2 + (n * (n - 1)) / a + 1;
return 0;
}
if (r == 4) {
cout << (n * (n - 1) * (n - 2) * (n - 3)) / c * 9 +
(n * (n - 1) * (n - 2)) / b * 2 + (n * (n - 1) / a) + 1;
return 0;
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int n, k;
int main() {
cin >> n >> k;
if (k == 1) {
cout << 1 << '\n';
return 0;
}
if (k == 2) {
cout << (n * (n - 1)) / 2 + 1 << '\n';
return 0;
}
if (k == 3) {
long long int p = 4;
long long int ans = 15;
for (int i = 4; i < n; i++) {
ans += p * p;
p++;
}
cout << ans << '\n';
return 0;
}
long long int ans = 24;
long long int c = 4, p = 13, add = 10;
for (long long int i = 4; i < n; i++) {
ans += c * p;
c++;
p += add;
add += 3;
}
cout << ans << '\n';
}
|
#include <bits/stdc++.h>
using namespace std;
int arr[26];
int main() {
long long int n, k;
cin >> n >> k;
if (k == 1) {
cout << 1;
}
if (k == 2) {
int64_t sup = ((n) * (n - 1)) / 2 + 1;
cout << sup;
}
if (k == 3) {
int64_t sup = ((n) * (n - 1) * (n - 2)) / 3 + ((n) * (n - 1)) / 2 + 1;
cout << sup;
}
if (k == 4) {
int64_t sup = 3 * ((n) * (n - 1) * (n - 2) * (n - 3)) / 8 +
((n) * (n - 1) * (n - 2)) / 3 + ((n) * (n - 1)) / 2 + 1;
cout << sup;
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1005;
int n, k;
int d[] = {1, 0, 1, 2, 9};
long long res;
long long f[5][maxn];
long long tohop(int x, int y) {
if (x == 0) return 1;
if (x == y) return 1;
if (f[x][y] != 0) return f[x][y];
f[x][y] = tohop(x - 1, y - 1) + tohop(x, y - 1);
return f[x][y];
}
int main() {
cin >> n >> k;
for (int i = 0; i <= k; i++) res += d[i] * tohop(i, n);
cout << res;
}
|
#include <bits/stdc++.h>
using namespace std;
const int MAX = 1234;
long long D[MAX];
long long C(int n, int k) {
long long n_fat = 1LL;
long long baixo = 1LL;
long long aux = 1LL;
for (long long i = n; i > k; i--) {
n_fat *= i;
baixo *= aux++;
}
return n_fat / baixo;
}
void init(int n) {
D[0] = 1, D[1] = 0, D[2] = 1;
for (int i = 3; i <= n; i++) {
D[i] = (i - 1) * 1LL * (D[i - 1] + D[i - 2]);
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, k;
cin >> n >> k;
init(n);
long long ans = 0LL;
for (int i = n - k; i <= n; i++) {
ans += (C(n, i) * D[n - i] * 1LL);
}
cout << ans << "\n";
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1001;
long long dp[maxn][maxn];
int d[maxn];
int n;
int k;
int main() {
ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
cin >> n >> k;
d[0] = 1;
d[1] = 0;
d[2] = 1;
d[3] = 2;
for (int i = 4; i < maxn; i++) {
d[i] = (i - 1) * (d[i - 1] + d[i - 2]);
}
dp[1][1] = 1;
dp[1][0] = 1;
for (int i = 2; i <= 1000; i++) {
for (int j = 0; j <= i; j++) {
if (j == 0) {
dp[i][j] = 1;
} else {
dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1];
}
}
}
long long int ans = 0;
for (int i = n - k; i <= n; i++) {
ans += d[n - i] * dp[n][n - i];
}
cout << ans;
}
|
#include <bits/stdc++.h>
using namespace std;
inline long long read() {
long long t = 0, f = 1;
char c = getchar();
while (c < '0' || c > '9') {
if (c == '-') f = -1;
c = getchar();
}
while (c >= '0' && c <= '9') t = t * 10 + c - 48, c = getchar();
return t * f;
}
long long n, k, ar = 1;
int main() {
n = read();
k = read();
if (k >= 2) ar += n * (n - 1) / 2;
if (k >= 3) ar += n * (n - 1) * (n - 2) / 3;
if (k >= 4) ar += n * (n - 1) * (n - 2) * (n - 3) * 3 / 8;
cout << ar;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int M = 5e6 + 5;
const long long int mod = 1e9 + 7;
const long long int inf = 9e18;
const double pi = 3.14159265358979323846;
long long int t, n, m, x, sum, k, p, u = 0;
string s, z, ans = "";
long long int P[10000005] = {0};
void sieve() {
for (long long int i = 2; i < (10000005); i++)
if (!P[i])
for (long long int j = i * i; j < (10000005); j += i) P[j] = i;
}
long long int raised(long long int x, long long int v) {
if (v == 0) return 1 % mod;
if (v % 2 == 1) return (x * raised(x, v - 1)) % mod;
long long int r = raised(x, v / 2);
return (r * r) % mod;
}
bool prime(long long int n) {
if (n == 1) return 1;
for (int i = 2; i <= sqrt(n); i++)
if (n % i == 0) return 0;
return 1;
}
long long int hcf(long long int a, long long int b) {
if (a % b == 0) return b;
return hcf(b, a % b);
}
bool comp(long long int a, long long int b) { return (a < b); }
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
;
long long int t1 = 1;
cin >> n >> k;
cout << 1 + (k > 1) * (n * (n - 1)) / 2 +
(k > 2) * (n * (n - 1) * (n - 2)) / 3 +
9 * (k > 3) * (n * (n - 1) * (n - 2) * (n - 3)) / 24;
}
|
#include <bits/stdc++.h>
const long long N = 1e3 + 10;
const long long inf = 2e5 + 100;
const long long mod = 1e9 + 7;
using namespace std;
long long fact[N];
long long ncr(long long n, long long k) {
long long num = 1;
long long denom = 1;
for (int i = n; i >= n - k + 1; i--) {
num *= i;
}
for (int i = 1; i <= k; i++) {
denom *= (i);
}
return num / denom;
}
long long derange(long long n) {
switch (n) {
case 0:
return 1;
case 1:
return 0;
case 2:
return 1;
case 3:
return 2;
case 4:
return 9;
}
return 0;
}
int main() {
fact[0] = 1;
for (int i = 1; i < N; i++) {
fact[i] = (i * fact[i - 1]) % mod;
}
long long n, k;
cin >> n >> k;
long long ans = 0;
for (int i = n; i >= n - k; i--) {
ans += ncr(n, n - i) * derange(n - i);
}
cout << ans << "\n";
}
|
#include <bits/stdc++.h>
int main() {
long long n, k, ans;
scanf("%lld %lld", &n, &k);
if (k >= 1) ans = 1;
if (k >= 2) ans = ans + n * (n - 1) / 2;
if (k >= 3) ans = ans + n * (n - 1) * (n - 2) / 3 / 2 * 2;
if (k >= 4) ans = ans + n * (n - 1) * (n - 2) * (n - 3) / 4 / 3 / 2 * 9;
printf("%lld\n", ans);
}
|
#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5 + 37;
long long int c[1037][1037];
int main() {
for (int i = 0; i < 1037; i++) {
c[i][0] = 1;
for (int j = 1; j < i + 1; j++) {
c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
}
}
int n, k;
cin >> n >> k;
int pole[5] = {0, 0, 1, 2, 9};
long long int vys = 1;
for (int i = 2; i < k + 1; i++) {
vys += c[n][i] * pole[i];
}
cout << vys << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int func1(long long int n, long long int k) {
long long int i, val = 1;
for (i = 0; i < k; i++) {
val = val * (n - i);
}
for (i = 1; i <= k; i++) {
val = val / i;
}
return val;
}
long long int func2(long long int k) {
if (k == 0)
return 1;
else if (k == 1)
return 0;
else if (k == 2)
return 1;
else if (k == 3)
return 2;
else if (k == 4)
return 9;
}
int main() {
long long int n, i, k, ans = 0;
cin >> n >> k;
for (i = 0; i <= k; i++) {
ans += func1(n, i) * func2(i);
}
cout << ans << endl;
}
|
#include <bits/stdc++.h>
using namespace std;
long long Det[20000];
long long C[2000];
void det() {
Det[0] = 1;
Det[1] = 0;
Det[2] = 1;
for (long long i = 3; i <= 10009; i++) {
Det[i] = (i - 1) * (Det[i - 1] + Det[i - 2]);
}
}
long long binomialCoeff(long long n, long long k) {
memset(C, 0, sizeof(C));
C[0] = 1;
for (long long i = 1; i <= n; i++) {
for (long long j = min(i, k); j > 0; j--) C[j] = C[j] + C[j - 1];
}
return C[k];
}
int main() {
long long i, j, k, l, m, n, ans = 0;
det();
cin >> n >> k;
m = n - k;
for (i = m; i <= n; i++) {
ans += (binomialCoeff(n, i) * Det[n - i]);
}
cout << ans << endl;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
;
cin.tie(0);
;
long long int n, k, ans = 0;
cin >> n >> k;
if (k == 1) {
cout << "1";
return 0;
}
if (k == 2) {
ans = 1 + (n * (n - 1)) / 2;
cout << ans;
return 0;
}
if (k == 3) {
ans = 1 + (n * (n - 1)) / 2 + (n * (n - 1) * (n - 2)) / 3;
cout << ans;
return 0;
}
ans = 1 + (n * (n - 1)) / 2 + (n * (n - 1) * (n - 2)) / 3 +
(9 * n * (n - 1) * (n - 2) * (n - 3)) / 24;
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
inline bool isvowel(char ch) {
ch = tolower(ch);
return (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u' ||
ch == 'y');
}
inline bool isprime(int n) {
if (n < 2 || (n % 2 == 0 && n != 2)) return false;
for (int i = 3; i * i <= n; i += 2)
if (n % i == 0) return false;
return true;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
long long n, k, cnt = 0, i, j;
cin >> n >> k;
for (i = k; i >= 0; i--) {
long long sum = 1;
for (j = 0; j < i; j++) {
sum *= n - j;
}
for (j = 2; j <= i; j++) {
sum /= j;
}
if (i == 1)
sum = 0;
else if (i == 3)
sum *= 2;
else if (i == 4)
sum *= 9;
cnt += sum;
}
cout << cnt;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long n, k;
cin >> n >> k;
long long ans = 0;
for (int i = 1; i <= k; i++) {
if (i == 1)
ans++;
else if (i == 2)
ans += n * (n - 1) / 2;
else if (i == 3)
ans += n * (n - 1) * (n - 2) / 6 * 2;
else
ans += n * (n - 1) * (n - 2) * (n - 3) / 24 * 9;
}
cout << ans << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1010;
long long n, k;
long long ans[5];
long long A(long long bot, long long top) {
long long ret = 1;
for (long long i = 0; i < top; ++i) ret *= bot - i;
return ret;
}
long long C(long long bot, long long top) {
long long up = 1, down = 1;
for (long long i = 0; i < top; ++i) up *= bot - i;
for (long long i = 2; i <= top; ++i) down *= i;
return up / down;
}
int main() {
while (~scanf("%I64d%I64d", &n, &k)) {
ans[1] = 1;
ans[2] = ans[1] + A(n, 2) - C(n, 2);
ans[3] = ans[2] + A(n, 3) - C(n, 3) * (1 + C(3, 1));
ans[4] = ans[3] + A(n, 4) - C(n, 4) * (1 + C(4, 3) + C(4, 2) + C(4, 1));
printf("%I64d\n", ans[k]);
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long f[1005][5];
int n, k;
int main() {
ios::sync_with_stdio(0), cin.tie(0);
f[0][0] = 1;
for (int i = 1; i <= 1000; i++) {
f[i][0] = 1;
f[i][1] = 0;
for (int j = 2; j <= 4; j++)
f[i][j] = f[i - 1][j] + f[i - 1][j - 1] * (j - 1) +
f[i - 1][j - 2] * (i - j + 1);
}
while (cin >> n >> k) {
long long ans = 0;
for (int i = 0; i < (k + 1); ++i) ans += f[n][i];
cout << ans << endl;
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long n, K;
long long v[100002];
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> K;
K = min(n, K);
long long res = 0;
res++;
long long fact = 1LL, aux = 1LL, aux2;
for (int k = 1; k <= K; k++) {
fact *= k;
aux *= (n - k + 1);
aux2 = (long long)aux / fact;
res += aux2 * (k == 1 ? 0 : k == 2 ? 1 : k == 3 ? 2 : 9);
}
cout << res << "\n";
}
|
#include <bits/stdc++.h>
using namespace std;
const long long N = 1e5 + 1, MAX = 10;
const long long MOD = 1e9 + 7, mod = 1e6 + 3;
long long f[6] = {1, 1, 2, 6, 24, 120};
long long nCr(long long n, long long r) {
long long ans = 1;
long long diff = n - r;
for (long long i = n; i > diff; i--) ans = ans * i;
ans = ans / f[r];
return ans;
}
long long dear(long long n) {
long long ans = f[n], flag = -1;
for (long long i = 1; i <= n; i++) {
long long curr = flag * f[i];
ans = ans + f[n] / curr;
flag = flag * -1;
}
return ans;
}
void solve() {
long long n, m, j, i, k, r, l, x, y;
cin >> n >> k;
long long ans = 0, fact = 1;
for (long long i = 0; i <= k; i++) {
ans += (nCr(n, i) * dear(i));
}
cout << ans << endl;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
long long t = 1;
while (t--) solve();
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
inline long long int c(long long int n, long long int i) {
if (i == 0)
return 1;
else if (i == 1)
return n;
else if (i == 2)
return (n * (n - 1)) / 2;
else if (i == 3)
return (n * (n - 1) * (n - 2)) / 6;
else if (i == 4)
return (n * (n - 1) * (n - 2) * (n - 3)) / 24;
}
int main() {
long long int d[5];
d[0] = 1;
d[1] = 0;
d[2] = 1;
d[3] = 2;
d[4] = 9;
long long int n, k;
cin >> n >> k;
long long int ans = 0;
for (long long int i = 0; i <= k; i++) ans += d[i] * c(n, i);
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const long long MOD = (long long)1e9 + 7;
const long long N = 1e3 + 5, inf = 1e9 + 5;
long long add(long long x, long long y) {
x += y;
if (x >= MOD) return x - MOD;
return x;
}
long long sub(long long x, long long y) {
x -= y;
if (x < 0) return x + MOD;
return x;
}
long long mult(long long x, long long y) { return (x * y) % MOD; }
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
long long choose(long long n, long long k) {
if (k == 0) return 1;
return (n * choose(n - 1, k - 1)) / k;
}
long long derange(long long n) {
if (n == 1) return 0;
if (n == 0) return 1;
return (n - 1) * (derange(n - 1) + derange(n - 2));
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
long long n, k;
cin >> n >> k;
long long ans = 0;
for (int i = 0; i <= k; ++i) {
ans += choose(n, i) * derange(i);
}
cout << ans << endl;
}
|
#include <bits/stdc++.h>
using namespace std;
long long get(long long n, long long k) {
if (k == 1) return 0;
if (k == 2) {
return n * (n - 1) / 2;
}
if (k == 3) {
return n * (n - 1) * (n - 2) / 6 * 2;
}
if (k == 4) {
return (long long)n * (n - 1) * (n - 2) * (n - 3) / 24 * (6 + 3);
}
return 0;
}
void solve(long long tz) {
long long n, k;
cin >> n >> k;
long long a[n];
for (long long i = 0; i < n; i++) {
a[i] = i + 1;
}
long long cnt = 0;
long long A[1001] = {0};
long long last = 1;
long long num = 0;
for (long long i = 0; i < 1001; i++) {
A[i] = last + num;
last = A[i];
num++;
}
long long B[1001] = {0};
last = 1;
num = 1;
for (long long i = 0; i < 1001; i++) {
B[i] = last + (num - 1) * (num - 1);
last = B[i];
num++;
}
if (k == 1) {
cout << 1 << endl;
return;
} else if (k == 2) {
cout << A[n - 1] << endl;
return;
} else if (k == 3) {
cout << B[n - 1] << endl;
return;
} else if (k == 4) {
long long ans = 1;
for (int i = 1; i <= k; i++) {
ans += get(n, i);
}
cout << ans << endl;
return;
}
}
int main() {
long long t;
t = 1;
long long z = 0;
while (t--) {
z++;
solve(z);
}
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long n, k;
cin >> n >> k;
long long ans = 1;
if (k >= 2) {
ans += n * (n - 1) / 2;
}
if (k >= 3) {
ans += n * (n - 1) * (n - 2) / 3;
}
if (k >= 4) {
ans += n * (n - 1) * (n - 2) * (n - 3) / 24 * 9;
}
cout << ans;
}
|
#include <bits/stdc++.h>
using namespace std;
int n, k;
long long c[5];
int a[5];
int main() {
scanf("%d%d", &n, &k);
c[1] = n;
a[2] = 1;
a[3] = 2;
a[4] = 9;
for (int i = 2; i <= 4; i++) {
c[i] = c[i - 1] * (n - (i - 1)) / i;
}
long long ans = 1;
for (int i = 2; i <= k; i++) {
ans += a[i] * c[i];
}
printf("%lld\n", ans);
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1000 + 100;
int n, k;
long long C[maxn][maxn];
void Init() {
C[0][0] = 1;
for (int i = 1; i < maxn; ++i) {
for (int j = 0; j <= i; ++j) {
if (j == 0 || j == i) {
C[i][j] = 1;
} else {
C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
}
}
}
}
int main() {
ios::sync_with_stdio(false);
Init();
while (scanf("%d%d", &n, &k) != EOF) {
long long ans = 0;
if (k >= 1) {
ans += 1;
}
if (k >= 2) {
ans += C[n][2];
}
if (k >= 3) {
ans += C[n][3] * 2;
}
if (k >= 4) {
ans += C[n][4] * 9;
}
printf("%I64d\n", ans);
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long n, k;
long long ans = 1;
int main() {
cin >> n >> k;
if (k >= 2) ans += n * (n - 1) / 2;
if (k >= 3) ans += 2 * n * (n - 1) * (n - 2) / 6;
if (k >= 4) ans += 9 * n * (n - 1) * (n - 2) * (n - 3) / 24;
cout << ans << endl;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(NULL);
cout.tie(NULL);
long long n, k, c, ans = 1;
cin >> n >> k;
for (int i = 2; i <= k; i++) {
c = 1;
for (int j = 0; j < i; j++) {
c *= n - j;
}
for (int j = 2; j <= i; j++) {
c /= j;
}
if (i == 3) {
c *= 2;
}
if (i == 4) {
c *= 9;
}
ans += c;
}
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1e9 + 7;
long long int binomialCoeff(long long int n, long long int k) {
long long int res = 1;
if (k > n - k) k = n - k;
for (long long int i = 0; i < k; ++i) {
res *= (n - i);
res /= (i + 1);
}
return res;
}
long long int countDer(long long int n) {
if (n == 1) return 0;
if (n == 0) return 1;
if (n == 2) return 1;
return (n - 1) * (countDer(n - 1) + countDer(n - 2));
}
int main() {
long long int n, k;
cin >> n >> k;
long long int ans = 0;
for (long long int i = 0; i <= k; i++)
ans += (long long int)countDer(i) * (long long int)binomialCoeff(n, i);
return cout << ans, 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1000 + 100;
int n, k;
long long C[maxn][maxn];
void Init() {
C[0][0] = 1;
for (int i = 1; i < maxn; ++i) {
for (int j = 0; j <= i; ++j) {
if (j == 0 || j == i) {
C[i][j] = 1;
} else {
C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
}
}
}
}
int main() {
ios::sync_with_stdio(false);
Init();
scanf("%d%d", &n, &k);
long long ans;
if (k == 1) {
ans = 1;
} else if (k == 2) {
ans = C[n][2] + 1;
} else if (k == 3) {
ans = C[n][3] * 2 + C[n][2] + 1;
} else {
ans = C[n][4] * 9 + C[n][3] * 2 + C[n][2] + 1;
}
printf("%I64d\n", ans);
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long ans = 1, n, m;
scanf("%I64d%I64d", &n, &m);
if (m > 1) ans = ans + n * (n - 1) / 2;
if (m > 2) ans = ans + n * (n - 1) * (n - 2) / 3;
if (m > 3) ans = ans + n * (n - 1) * (n - 2) * (n - 3) * 3 / 8;
printf("%I64d\n", ans);
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long n, k;
cin >> n >> k;
if (k == 1)
cout << "1\n";
else if (k == 2) {
long long ans = 7;
for (int i = 4; i < n; i++) ans += i;
cout << ans << endl;
} else if (k == 3) {
long long ans = 15;
for (int i = 4; i < n; i++) ans += i * i;
cout << ans << endl;
} else {
long long f = 24;
for (int x = 4; x < n; x++) {
long long n = x - 3;
long long ans = 3 * (n * n * n) + 20 * (n * n) + 45 * n + 18 * 2;
ans /= 2;
f += ans;
}
cout << f << endl;
}
}
|
#include <bits/stdc++.h>
using namespace std;
const long long MAX5 = 1e+5 + 7;
const long long MAX7 = 1e+7 + 7;
const long long MAXN = MAX7;
const long long INF = 0x7f7f7f7f7f7f7f7f;
const int INFi = 0x7f7f7f7f;
const long long MOD = 1e9 + 7;
long long T = 1;
long long n, x, k, p, m, y;
string second, t;
long double w;
vector<long long> de;
long long NCR(long long n, long long r) {
if (n < r) return 0;
if (r == 0) return 1;
if (r > n / 2) return NCR(n, n - r);
long long res = 1;
for (long long k = 1; k <= r; ++k) {
res *= n - k + 1;
res /= k;
}
return res;
}
void deg() {
de[0] = 1;
de[1] = 0;
de[2] = 1;
for (long long i = 3; i <= k; i++) {
de[i] = (i - 1) * (de[i - 1] + de[i - 2]);
}
}
void MAIN() {
cin >> n >> k;
de = vector<long long>(k + 1);
deg();
long long ans = 0;
for (long long i = 0; i <= k; i++) {
ans += de[i] * NCR(n, i);
}
cout << ans;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cout << fixed;
cout << setprecision(12);
;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
;
while (T--) {
MAIN();
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int get(long long int n) {
if (n == 0) return 1;
if (n == 1) return 0;
if (n == 2) return 1;
if (n == 3) return 2;
if (n == 4) return 9;
}
long long int ncr(long long int n, long long int c) {
long long int t = 1;
c = min(c, n - c);
for (long long int i = 1; i <= c; i++) t = (t * (n - i + 1)) / i;
return t;
}
int main() {
long long int n, k;
cin >> n >> k;
long long int ans = 0;
for (long long int i = 0; i <= k; i++) {
ans += (ncr(n, i) * get(i));
}
cout << ans;
}
|
#include <bits/stdc++.h>
using namespace std;
long long dp[1005][5];
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
dp[1][0] = 1;
int n, k;
cin >> n >> k;
for (int i = 2; i <= n; i++) {
for (int j = 0; j <= k && j <= i; j++) {
dp[i][j] += dp[i - 1][j];
if (j) {
dp[i][j] += (j - 1) * dp[i - 1][j - 1];
}
if (j > 1) {
dp[i][j] += (i - j + 1) * dp[i - 1][j - 2];
}
}
}
long long ans = 0;
for (int i = 0; i <= k; i++) {
ans += dp[n][i];
}
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
long long int n, k;
cin >> n >> k;
long long int ans = 1;
if (k >= 2) ans += (n * (n - 1)) / 2;
if (k >= 3) ans += ((n * (n - 1) * (n - 2)) / 6) * 2;
if (k >= 4) ans += ((n * (n - 1) * (n - 2) * (n - 3)) / 24) * 9;
cout << ans << "\n";
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long calc(long long n, long long k) {
long long a = 1, b = 1, c;
for (long long i = 1; i <= k; i++) a = a * (n - i + 1), b = b * i;
if (k == 4)
c = 9;
else if (k == 3)
c = 2;
else if (k == 2)
c = 1;
else
c = 0;
return c * a / b;
}
int main() {
long long n, k;
cin >> n >> k;
long long res = 0;
while (k) res += calc(n, k--);
cout << res + 1;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
unsigned long long n, k;
unsigned long long C(unsigned long long n, unsigned long long k) {
unsigned long long ans = 1;
for (unsigned long long i = 1; i <= k; i++) {
ans *= (n - i + 1);
}
for (unsigned long long i = 1; i <= k; i++) {
ans /= (k - i + 1);
}
return ans;
}
int main() {
cin >> n >> k;
if (k == 1)
cout << 1 << endl;
else if (k == 2)
cout << C(n, 2) + 1 << endl;
else if (k == 3)
cout << C(n, 3) * 2 + C(n, 2) + 1 << endl;
else if (k == 4)
cout << C(n, 4) * 9 + C(n, 3) * 2 + C(n, 2) + 1 << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int C(int n, int r) {
long long int ans = 1;
for (int i = 0; i < r; ++i) {
ans = (ans * (n - i));
}
for (int i = 2; i <= r; ++i) {
ans /= i;
}
return ans;
}
int main() {
int n, k;
long long int ans = 1;
scanf("%d", &n), scanf("%d", &k);
for (int i = 2; i <= k; ++i) {
ans += (C(n, i) * pow(i - 1, i - 2));
}
printf("%lld\n", ans);
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long n, k;
long long mem[2000][2000];
long long C(long long n, long long k) {
if (mem[n][k] != -1) return mem[n][k];
if (k > n / 2) k = n - k;
if (k == 1) return n;
if (k == 0) return 1ll;
return mem[n][k] = C(n - 1, k) + C(n - 1, k - 1);
}
long long fact(long long n) {
long long ret = 1;
for (long long i = 1; i <= n; i++) ret *= i;
return ret;
}
long long subFact(long long n) {
long long f = fact(n);
long long sum = 0;
for (int k = 0; k <= n; k++) {
if (k % 2 == 0)
sum += f / fact(k);
else
sum -= f / fact(k);
}
return sum;
}
long long ans(long long n, long long k) {
long long ret = 0;
for (long long i = n - k; i <= n; i++) {
ret += C(n, i) * subFact(n - i);
}
return ret;
}
int main() {
for (int i = 0; i < 2000; i++)
for (int j = 0; j < 2000; j++) mem[i][j] = -1;
cin >> n >> k;
cout << ans(n, k);
}
|
#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const double PI = acos(-1);
const double EPS = 1e-6;
const int INF = 0x3f3f3f3f;
inline void read(long long& x) {
int f = 1;
char c;
while (((c = getchar()) < '0' || c > '9') && c != '-')
;
c == '-' ? (f = -1, x = 0) : (x = c - '0');
while ((c = getchar()) >= '0' && c <= '9') x = x * 10 + c - '0';
x *= f;
}
inline void read(int& x) {
long long t;
read(t);
x = t;
}
int main() {
long long n, k;
read(n);
read(k);
long long ans = 1;
if (k >= 2) ans += n * (n - 1) / 2;
if (k >= 3) ans += n * (n - 1) * (n - 2) / 3;
if (k >= 4) ans += n * (n - 1) / 2 * (n - 2) / 3 * (n - 3) / 4 * 9;
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long unorder(int n) {
if (n == 0) return 1;
if (n == 1) return 0;
bool good;
long long ans = 0;
vector<int> V(n);
for (int i = 0; i < n; i++) V[i] = i;
do {
good = true;
for (int i = 0; i < n && good; i++) good = (V[i] != i);
if (good) ans++;
} while (next_permutation(V.begin(), V.end()));
return ans;
}
long long newton(int n, int k) {
if (k > n) return 0;
if (2 * k > n) k = n - k;
long long ans = 1;
for (int i = n - k + 1; i <= n; i++) ans *= i;
for (int i = 1; i <= k; i++) ans /= i;
return ans;
}
int main() {
int n, k;
long long ans = 0;
cin >> n >> k;
for (int i = 0; i <= k; i++) {
long long unorders = unorder(i), combinations = newton(n, n - i);
ans += combinations * unorders;
}
cout << ans << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
signed main() {
long long int n, k;
cin >> n >> k;
long long int sum = 0;
long long int c[5];
long long int mul[5];
mul[4] = 9;
mul[3] = 2;
mul[2] = 1;
mul[1] = 1;
long long int x = 1;
long long int y = n;
long long int f = 1;
for (long long int i = 1; i <= 4; i++) {
f = f * y;
x = x * i;
c[i] = f / x;
y--;
}
if (n == k)
cout << "24" << endl;
else {
for (long long int i = 2; i <= k; i++) sum = sum + mul[i] * c[i];
sum++;
cout << sum << "\n";
}
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
template <typename t>
t in(t q) {
cin >> q;
return q;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
os << "[";
for (int i = 0; i < ((int)size(v)); ++i) {
os << v[i];
if (i != ((int)size(v)) - 1) os << ",";
}
os << "]\n";
return os;
}
template <typename T, typename S>
ostream& operator<<(ostream& os, const map<T, S>& v) {
for (auto it : v) os << it.first << ":" << it.second << "\n";
return os;
}
template <typename T, typename S>
ostream& operator<<(ostream& os, const pair<T, S>& v) {
os << "(";
os << v.first << "," << v.second << ")";
return os;
}
const int OO = (int)1e9;
const double PI = acos(-1);
const int N = 100005;
long long solve(long long n, long long k) {
if (k == 0) return 1;
if (k == 1) return solve(n, k - 1);
if (k == 2) return n * (n - 1) / 2 * 1 + solve(n, k - 1);
if (k == 3) return n * (n - 1) * (n - 2) / 6 * 2 + solve(n, k - 1);
if (k == 4) return n * (n - 1) * (n - 2) * (n - 3) / 24 * 9 + solve(n, k - 1);
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
long long n, k;
cin >> n >> k;
cout << solve(n, k);
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long ncr(int n, int r) {
if (n == r) return 1;
r = min(n - r, r);
long long ans = 1ll;
for (int i = 0; i < r; i++) {
ans = ans * (n - i) / (i + 1);
}
return ans;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, k;
cin >> n >> k;
long long ans = 1ll;
int x = n - k;
vector<long long> dp(k + 1, 0);
dp[0] = 0;
dp[1] = 0;
dp[2] = 1;
vector<long long> fact(k + 1, 0);
fact[2] = 2ll;
for (int i = 3; i <= k; i++) {
fact[i] = i * fact[i - 1];
dp[i] = fact[i] - 1;
for (int j = 1; j <= (i - 2); j++) {
dp[i] -= ncr(i, j) * dp[i - j];
}
}
for (int i = x; i <= n; i++) {
long long nci = ncr(n, i);
ans += nci * dp[n - i];
}
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
int n, k;
cin >> n >> k;
double ans;
if (k == 1) {
ans = 1;
} else if (k == 2) {
ans = 1 + (double)(n * (n - 1)) / 2;
} else if (k == 3) {
ans = 1 + (double)(n * (n - 1)) / 2 + (double)(n * (n - 1) * (n - 2)) / 3;
} else if (k == 4) {
ans = 1 + (double)(n * (n - 1)) / 2 + (double)(n * (n - 1) * (n - 2)) / 3 +
(((double)(n * (n - 1)) / 4) * (((n - 2) * (n - 3)) / 2)) * 3;
}
printf("%lld", (long long)(ans + 0.01));
return 0;
}
|
#include <bits/stdc++.h>
const int Inf = 1e9;
long long LINF = (long long)4e18;
const long long mod = 1e9 + 7;
using namespace std;
long long soch(long long n, long long k) {
long long ans = 1;
long long tmp = 1;
for (int(i) = n - k + 1; (i) < n + 1; (i)++) ans *= (long long)i;
for (int(i) = 2; (i) < k + 1; (i)++) tmp *= (long long)i;
return ans / tmp;
}
int main() {
ios::sync_with_stdio(false);
long long n, k;
cin >> n >> k;
long long ans = 1;
for (int(i) = n - k; (i) < n - 1; (i)++) {
ans += soch(n, n - i) * (long long)pow(n - i - 1, n - i - 2);
}
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long n, k, sol;
cin >> n >> k;
if (k == 1) sol = 1;
if (k == 2) sol = 1 + n * (n - 1) / 2;
if (k == 3) sol = 1 + n * (n - 1) / 2 + 2 * n * (n - 1) * (n - 2) / 6;
if (k == 4)
sol = 1 + n * (n - 1) / 2 + 2 * n * (n - 1) * (n - 2) / 6 +
9 * n * (n - 1) * (n - 2) * (n - 3) / 24;
cout << sol;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }
const int MAXN = 1000;
int n, mxdiff;
void run() {
scanf("%d%d", &n, &mxdiff);
long long ret = 0;
for (int ndiff = (0); ndiff <= (mxdiff); ++ndiff) {
if (ndiff == 0) ret += 1;
if (ndiff == 2) ret += (long long)n * (n - 1) / 2;
if (ndiff == 3) ret += ((long long)n * (n - 1) * (n - 2) / 6) * 2;
if (ndiff == 4)
ret += ((long long)n * (n - 1) * (n - 2) * (n - 3) / 24) * (3 + 6);
}
printf("%lld\n", ret);
}
int main() {
run();
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long n = 0;
long long k = 0;
long long wynik = 0;
long long wynik2 = 0;
long long wynik3 = 0;
cin >> n >> k;
if (k == 1) {
cout << "1";
return 0;
}
if (k == 2) {
wynik = n * (n - 1) / 2 + 1;
cout << wynik;
return 0;
}
if (k == 3) {
wynik = n * (n - 1) / 2;
wynik2 = n * (n - 1) * (n - 2) / 3 + 1;
cout << wynik2 + wynik;
return 0;
}
if (k == 4) {
wynik = n * (n - 1) / 2;
wynik2 = n * (n - 1) * (n - 2) / 3 + 1;
wynik3 = (n * (n - 1) * (n - 2) * (n - 3) / 24) * 9;
cout << wynik + wynik2 + wynik3;
}
}
|
#include <bits/stdc++.h>
using namespace std;
long long C(long long n, long long m) {
long long res = 1;
for (long long i = n; i > n - m; i--) res *= i;
for (long long i = m; i >= 1; i--) res /= i;
return res;
}
int main() {
ios::sync_with_stdio(0), cin.tie(0);
long long n, k, res = 1;
cin >> n >> k;
if (k >= 2) res += C(n, 2);
if (k >= 3) res += C(n, 3) * 2;
if (k >= 4) res += C(n, 4) * 9;
cout << res << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long f[1005], c[1005][1005];
int main() {
f[1] = 0LL;
f[2] = 1LL;
f[0] = 1LL;
for (int i = 3; i < 1005; i++) f[i] = (i - 1) * (f[i - 1] + f[i - 2]);
c[1][0] = c[1][1] = 1;
for (int i = 2; i < 1005; i++) {
c[i][0] = 1;
for (int j = 1; j < 1005; j++) c[i][j] = c[i - 1][j] + c[i - 1][j - 1];
}
int n, k;
scanf("%d %d", &n, &k);
long long ans = 0LL;
for (int i = n - k; i <= n; i++) {
long long tmp = c[n][i] * f[n - i];
ans += tmp;
}
printf("%I64d\n", ans);
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const long long maxn = 1e5 + 2;
const long long M = 1e9 + 7;
const double eps = 1e-10;
long long calc(long long n, long long k) {
long long num = 1, denum = 1, derrangement;
for (int i = 1; i <= k; i++) denum *= (n - i + 1), num *= i;
if (k == 4)
derrangement = 9;
else if (k == 3)
derrangement = 2;
else if (k == 2)
derrangement = 1;
else
derrangement = 0;
return derrangement * (denum / num);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
long long n, k, res = 0;
cin >> n >> k;
for (int i = 0; i <= k; i++) res += calc(n, i);
cout << res + 1;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long dp[] = {1, 0, 1, 2, 9};
long long Cnk(long long n, long long k) {
long long res = 1;
if (k < 4) k = n - k;
for (long long i = n; i > k; i--) res *= (i);
for (long long i = 1; i <= n - k; i++) res /= i;
return res;
}
int main() {
long long n, k;
cin >> n >> k;
long long ans = 0;
for (long long i = n - k; i <= n; i++) {
ans += dp[n - i] * Cnk(n, i);
}
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int D[5] = {0, 0, 1, 2, 9};
map<pair<long long int, long long int>, long long int> store;
long long int NCR(long long int n, long long int r) {
if (n < r) return 0;
if (r == 0 || r == n) return 1;
long long int x, y;
if (store[make_pair(n - 1, r - 1)] != 0)
x = store[make_pair(n - 1, r - 1)];
else {
x = NCR(n - 1, r - 1);
store[make_pair(n - 1, r - 1)] = x;
}
if (store[make_pair(n - 1, r)] != 0)
y = store[make_pair(n - 1, r)];
else {
y = NCR(n - 1, r);
store[make_pair(n - 1, r)] = y;
}
return (x + y);
}
int main() {
long long int n, k;
cin >> n >> k;
long long int ans = 1;
while (k > 0) {
ans += ((NCR(n, k)) * (D[k]));
k--;
}
cout << ans << endl;
}
|
#include <bits/stdc++.h>
using namespace std;
const long long a[5] = {0, 0, 1, 2, 9};
long long n, k;
long long C(long long x, long long y) {
long long t = 1;
for (long long i = 1; i <= y; i++) t *= n - i + 1;
for (long long i = 1; i <= y; i++) t /= i;
return t;
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n >> k;
long long res = 1;
for (long long i = 2; i <= k; i++) res += C(n, i) * a[i];
cout << res << '\n';
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long int n, k;
cin >> n >> k;
if (k == 1) {
cout << 1;
} else if (k == 2)
cout << (n * (n - 1)) / 2 + 1;
else if (k == 3)
cout << (n * (n - 1)) / 2 + 1 + (2 * (n) * (n - 1) * (n - 2)) / 6;
else
cout << (n * (n - 1)) / 2 + 1 + (2 * (n) * (n - 1) * (n - 2)) / 6 +
(9 * (n) * (n - 1) * (n - 2) * (n - 3)) / 24;
}
|
#include <bits/stdc++.h>
using namespace std;
template <typename Arg1>
void __f(const char* name, Arg1&& arg1) {
cerr << name << ": " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args) {
const char* comma = strchr(names + 1, ',');
cerr.write(names, comma - names) << ": " << arg1 << " |";
__f(comma + 1, args...);
}
const int INF = 1 << 29;
const int MOD = 1e9 + 7;
long long comb(int n, int m) {
long long ret = 1;
for (int i = 1; i <= m; ++i) {
ret *= n - i + 1;
}
for (int i = 1; i <= m; ++i) {
ret /= i;
}
return ret;
}
int main() {
int n, m;
cin >> n >> m;
long long ret = 0;
if (m >= 0) {
++ret;
}
if (m >= 2) {
ret += comb(n, 2);
}
if (m >= 3) {
ret += comb(n, 3) * 2;
}
if (m >= 4) {
ret += comb(n, 4) * 9;
}
cout << ret << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int n, k;
int der[] = {1, 0, 1, 2, 9};
long long C(int n, int k) {
long long ans = 1;
for (int i = n; i > n - k; i--) ans *= i;
for (int i = 2; i <= k; i++) ans /= i;
return ans;
}
int main() {
ios::sync_with_stdio(false);
cin >> n >> k;
long long ans = 1;
for (int i = 0; i <= k; i++) ans += C(n, i) * der[i];
cout << ans - 1 << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long C(long long n, long long r) {
long long an = 1;
for (long long i = 0; i < r; ++i) {
an *= n - i;
}
for (long long i = 1; i <= r; ++i) {
an /= i;
}
return an;
}
int pp[5] = {1, 0, 1, 2, 9};
int main() {
long long n, k;
cin >> n >> k;
long long ans = 0;
for (int i = 0; i <= k; ++i) {
ans += C(n, i) * pp[i];
}
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int b(long long int n, long long int k) {
long long int res = 1;
if (k > n - k) k = n - k;
for (long long int i = 0; i < k; ++i) {
res *= (n - i);
res /= (i + 1);
}
return res;
}
int main() {
int n, k;
cin >> n >> k;
long long int ans = 1;
int j = k;
int a[3];
a[0] = 1;
a[1] = 2;
a[2] = 9;
k--;
int i = 0;
j = 2;
while (k--) {
ans += b(n, n - j) * a[i];
i++;
j++;
}
cout << ans << endl;
}
|
#include <bits/stdc++.h>
#pragma warning(disable : 4996)
#pragma comment(linker, "/STACK:336777216")
using namespace std;
const long long INF = 1e15 + 100;
const long long MOD = 1e9 + 7;
const long long INC = 1e15 + 100;
const long long EPS = 1e18 + 100;
const int N = 1000 * 1000 + 100;
long long minim = INF;
long long maxim = -INF;
long long cnt = 0, ans = 0;
vector<int> dp(N);
bool u = false, U[N];
int a[N], b[N], c[N];
int A[N / 1000][N / 1000];
string s, t;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
long long n, k;
cin >> n >> k;
ans = 1;
if (k >= 2) ans += (n * (n - 1)) * 1ll / 2;
if (k >= 3) ans += n * ((n - 1) * (n - 2)) * 1ll / 3;
if (k >= 4) ans += (n * (n - 1) * (n - 2) * (n - 3)) * 1ll * 9 / 24;
cout << ans << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
const long long inf = 3e18 + 5;
int add(int a, int b) { return (a += b) < mod ? a : a - mod; }
int mul(int a, int b) { return 1LL * a * b % mod; }
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, k;
cin >> n >> k;
const int d[] = {1, 0, 1, 2, 9};
long long res = 0;
for (int i = 0; i <= k; i++) {
long long add = 1;
for (int j = 0; j < i; j++) add *= (n - j);
for (int j = 1; j <= i; j++) add /= j;
res += add * d[i];
}
cout << res;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int dearr(long long int n) {
if (n == 0 || n == 1) {
return 0;
} else if (n == 2) {
return 1;
} else {
return ((n - 1) * (dearr(n - 1) + dearr(n - 2)));
}
}
long long int C(long long int n, long long int r) {
long long int a = n, b = 1;
for (long long int i = 1; i < r; i++) {
a *= (n - i);
b *= (i + 1);
}
return (a / b);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
long long int n, k;
cin >> n >> k;
long long int ans = 1;
for (long long int i = 0; i <= k; i++) {
ans += (C(n, i) * dearr(i));
}
cout << ans << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
long long n, k;
cin >> n >> k;
long long res = 1 + (k >= 2) * (n * (n - 1) / 2) * 1 +
(k >= 3) * (n * (n - 1) * (n - 2) / 6) * 2 +
(k >= 4) * (n * (n - 1) * (n - 2) * (n - 3) / 24) * 9;
cout << res;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long n, k, ans;
int main() {
cin >> n >> k;
ans += 1;
if (k >= 2) ans += n * (n - 1) / 2;
if (k >= 3) ans += n * (n - 1) * (n - 2) / 3;
if (k >= 4) ans += n * (n - 1) * (n - 2) * (n - 3) / 24 * 9;
cout << ans << endl;
}
|
#include <bits/stdc++.h>
using namespace std;
const int MAX = 200010;
const int MOD = 1000000007;
const int INF = 1e8;
const long long LLINF = 0x3f3f3f3f3f3f3f3f;
const long double EPS = 1e-7;
long long des[MAX];
long long solve(long long n, long long k) {
if (k == 1) {
return 1;
}
long long res = 1;
for (long long i = n - k + 1; i <= n; i++) {
res *= i;
}
for (long long i = 2; i <= k; i++) {
res /= i;
}
res *= des[k];
res += solve(n, k - 1);
return res;
}
int main() {
long long n, k;
cin >> n >> k;
des[0] = 1;
des[1] = 1;
for (long long i = 1; i < MAX; i++) {
des[i] = (i - 1) * (des[i - 1] + des[i - 2]);
}
cout << solve(n, k) << '\n';
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long C(int n, int k);
int main() {
int n, k;
while (scanf("%d%d", &n, &k) != EOF) {
if (k == 1)
printf("1\n");
else if (k == 2)
printf("%lld\n", C(n, 2) + 1);
else if (k == 3)
printf("%lld\n", C(n, 2) + 1 + C(n, 3) * 2);
else
printf("%lld\n", C(n, 2) + 1 + C(n, 3) * 2 + C(n, 4) * 9);
}
return 0;
}
long long C(int n, int k) {
long long ans = 1;
for (int i = n; i >= n - k + 1; i--) {
ans *= i;
}
for (int i = 1; i <= k; i++) {
ans /= i;
}
return ans;
}
|
#include <bits/stdc++.h>
using namespace std;
int n, k;
int used[1005], res[10];
long long ans, c[1005][10];
long long hes(int x, int y) {
long long res = 1;
int j = 1;
for (int i = x; i + y > x; i--) {
res *= i;
res /= j;
j++;
}
return res;
}
void comb() {
for (int i = 1; i <= n; i++) {
for (int j = 0; j <= k; j++) {
c[i][j] = hes(i, j);
}
}
}
void dfs(int now, int siz) {
if (now > siz) {
res[siz]++;
return;
}
for (int i = 1; i <= siz; i++) {
if (i == now) continue;
if (!used[i]) {
used[i] = 1;
dfs(now + 1, siz);
used[i] = 0;
}
}
}
void check(int siz) { dfs(1, siz); }
int main() {
scanf("%d %d", &n, &k);
res[0] = 1;
for (int i = 1; i <= 4; i++) {
check(i);
}
comb();
for (int i = 0; i <= k; i++) {
ans = ans + c[n][i] * res[i];
}
printf("%lld", ans);
}
|
#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const int N = 1234;
int n, k;
long long comb[N][N];
long long perms(int x) {
vector<int> v;
for (int i = 1; i <= x; i++) v.push_back(i);
int cnt = 0;
do {
bool ok = true;
for (int i = 0; i < (int)v.size(); i++)
if (v[i] == i + 1) ok = false;
if (ok) cnt++;
} while (next_permutation((v).begin(), (v).end()));
return cnt;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> n >> k;
comb[0][0] = 1;
for (int i = 1; i < N; i++) {
comb[i][0] = 1;
for (int j = 1; j < 5; j++) {
comb[i][j] = comb[i - 1][j] + comb[i - 1][j - 1];
}
}
long long ans = 1;
for (int i = 2; i <= k; i++) {
ans += comb[n][i] * perms(i);
}
cout << ans << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long n, k;
int main() {
cin >> n >> k;
if (k == 1) {
cout << 1;
}
if (k == 2) {
cout << n * (n - 1) / 2 + 1;
}
if (k == 3) {
cout << n * (n - 1) / 2 + 1 + (n - 2) * (n - 1) * n / 6 * 2;
}
if (k == 4) {
cout << n * (n - 1) / 2 + 1 + (n - 2) * (n - 1) * n / 6 * 2 +
9 * (n - 3) * (n - 2) * (n - 1) * n / 24;
}
}
|
#include <bits/stdc++.h>
using namespace std;
long long int mod = 998244353;
long long int f[2005][2005];
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
long long int t = 1;
while (t--) {
long long int n, k;
cin >> n >> k;
if (k == 1) {
cout << 1 << endl;
return 0;
}
if (k == 2) {
cout << 1 + (n * (n - 1)) / 2 << endl;
return 0;
}
if (k == 3) {
cout << 1 + (n * (n - 1)) / 2 + (n * (n - 1) * (n - 2)) / 3 << endl;
return 0;
}
if (k == 4) {
cout << 1 + (n * (n - 1)) / 2 + (n * (n - 1) * (n - 2)) / 3 +
(3 * (n * (n - 1) * (n - 2) * (n - 3))) / 8
<< endl;
}
}
}
|
#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
using namespace std;
bool check(vector<long long> a) {
for (long long i = 0; i < a.size(); i++) {
if (a[i] == i + 1) {
return false;
}
}
return true;
}
long long coun(long long n) {
if (n == 0) {
return 1;
}
vector<long long> a;
for (long long i = 1; i <= n; i++) {
a.push_back(i);
}
long long ans = 0;
while (next_permutation(a.begin(), a.end())) {
if (check(a)) {
ans++;
}
}
return ans;
}
signed main() {
long long i, j, n, k;
cin >> n >> k;
long long answer = 0;
for (i = n - k; i <= n; i++) {
long long ans = 1;
long long cur_k = n - i;
for (j = i + 1; j <= n; j++) {
ans *= j;
}
for (j = 1; j <= (n - i); j++) {
ans /= j;
}
ans *= coun(cur_k);
answer += ans;
}
cout << answer << '\n';
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long MOD = 1e9 + 7;
long long ncr(long long n, long long r) {
long long ans = 1;
for (long long i = 0; i < r; i++) ans *= n - i;
for (long long i = 0; i < r; i++) ans /= (i + 1);
return ans;
}
void solve() {
long long n, k;
cin >> n >> k;
long long d[5] = {1, 0, 1, 2, 9};
long long ans = 0;
if (n >= k) {
for (long long i = 0; i < k + 1; i++) {
ans += ncr(n, i) * d[i];
}
} else
ans = 1;
cout << ans << "\n";
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int t = 1;
while (t--) {
solve();
}
}
|
#include <bits/stdc++.h>
using namespace std;
long long derange(long long n) {
if (n == 0) {
return 1;
} else if (n == 1) {
return 0;
} else if (n == 2) {
return 1;
} else if (n == 3) {
return 2;
} else if (n == 4) {
return 9;
}
}
long long nCr(long long n, long long r) {
if (r == 0) {
return 1;
} else if (r == 1) {
return n;
} else if (r == 2) {
return (n * (n - 1)) / 2;
} else if (r == 3) {
return (n * (n - 1) * (n - 2)) / 6;
} else {
return (n * (n - 1) * (n - 2) * (n - 3)) / 24;
}
}
int main() {
long long n, k;
cin >> n >> k;
long long ans = 0;
for (long long i = 0; i <= k; i++) {
ans += (nCr(n, i) * derange(i));
}
cout << ans;
}
|
#include <bits/stdc++.h>
using namespace std;
inline void pisz(int n) { printf("%d\n", n); }
const int fx[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
const int fxx[9][2] = {{0, 0}, {0, 1}, {0, -1}, {1, 0}, {-1, 0},
{1, 1}, {1, -1}, {-1, 1}, {-1, -1}};
long long der[5] = {0, 0, 1, 2, 9};
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
long long n, k;
long long ans = 0;
cin >> n >> k;
for (long long i = 1; i <= k; i++) {
if (i == 1) {
ans += n * der[1];
} else if (i == 2) {
ans += ((n * (n - 1)) / 2) * der[2];
} else if (i == 3) {
ans += ((n * (n - 1) * (n - 2)) / 6) * der[3];
} else if (i == 4) {
ans += ((n * (n - 1) * (n - 2) * (n - 3)) / 24) * der[4];
}
}
cout << ans + 1;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
long long int C(long long int a, long long int b) {
long long int ret = 1;
for (int i = a; i > a - b; i--) {
ret *= i;
}
for (int i = 2; i <= b; i++) ret /= i;
return ret;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
long long int n, k, ans = 0;
cin >> n >> k;
long long int d[5] = {0, 0, 1, 2, 9};
for (int i = k; i >= 2; i--) {
ans += C(n, i) * d[i];
}
ans += 1;
cout << ans;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
int main() {
int n, k;
long long ans;
cin >> n >> k;
if (k == 1) ans = 1LL;
if (k == 2) ans = 1LL + (n * (n - 1LL)) / 2LL;
if (k == 3)
ans = 1LL + (n * (n - 1LL)) / 2LL + (n * (n - 1LL) * (n - 2LL)) / 3LL;
if (k == 4)
ans = 1LL + (n * (n - 1LL)) / 2LL + (n * (n - 1LL) * (n - 2LL)) / 3LL +
(3 * n * (n - 1LL) * (n - 2LL) * (n - 3LL)) / 8LL;
cout << ans << endl;
return 0;
}
|
#include <bits/stdc++.h>
using namespace std;
const int MOD = (int)1e9 + 7;
const long long INF = 1LL << 62;
const int inf = 1 << 30;
template <class T>
bool chmax(T& a, const T& b) {
if (a < b) {
a = b;
return 1;
}
return 0;
}
template <class T>
bool chmin(T& a, const T& b) {
if (b < a) {
a = b;
return 1;
}
return 0;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& V) {
int N = V.size();
for (int i = 0; i < (N); i++) {
os << V[i];
if (i != N - 1) os << " ";
}
os << "\n";
return os;
}
template <typename T, typename S>
ostream& operator<<(ostream& os, pair<T, S> const& P) {
os << "(";
os << P.first;
os << " , ";
os << P.second;
os << ")";
return os;
}
template <typename T>
ostream& operator<<(ostream& os, set<T>& S) {
auto it = S.begin();
while (it != S.end()) {
os << *it;
os << " ";
it++;
}
os << "\n";
return os;
}
template <typename T>
ostream& operator<<(ostream& os, deque<T>& q) {
for (auto it = q.begin(); it < q.end(); it++) {
os << *it;
os << " ";
}
os << endl;
return os;
}
template <typename T, typename S>
ostream& operator<<(ostream& os, map<T, S> const& M) {
for (auto e : M) {
os << e;
}
os << endl;
return os;
}
vector<pair<int, int>> dxdy = {make_pair(0, 1), make_pair(1, 0),
make_pair(-1, 0), make_pair(0, -1)};
long long choose(long long n, long long k) {
long long res = 1;
for (int i = 0; i < (k); i++) {
res *= n - i;
}
for (int i = 0; i < (k); i++) {
res /= i + 1;
}
return res;
}
bool is_ok(vector<int>& A) {
for (int i = 0; i < (A.size()); i++)
if (A[i] == i) return false;
return true;
}
long long solve(int N) {
vector<int> A(N);
for (int i = 0; i < (N); i++) A[i] = i;
long long res = 0;
while (next_permutation((A).begin(), (A).end())) {
res += is_ok(A);
}
return res;
}
int main() {
cin.tie(nullptr);
ios::sync_with_stdio(false);
int N, K;
cin >> N >> K;
long long ans = 0;
for (int k = 1; k <= K; k++) {
ans += choose(N, k) * solve(k);
}
cout << ans + 1 << endl;
}
|
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