p02879 AtCoder Beginner Contest 144 - 9x9
Problem Description
Having learned the multiplication table, Takahashi can multiply two integers between 1 and 9 (inclusive) together. He cannot do any other calculation.
Given are two integers A and B.
If Takahashi can calculate A \times B, print the result; if he cannot, print -1 instead.
Constraints
- 1 \leq A \leq 20
- 1 \leq B \leq 20
- All values in input are integers.
Input
Input is given from Standard Input in the following format:
A B
Output
If Takahashi can calculate A \times B, print the result; if he cannot, print -1.
Examples
Input
2 5
Output
10
Input
5 10
Output
-1
Input
9 9
Output
81
Contest Information
- Contest ID: 0
- Problem Index:
- Points: 0.0
- Rating: 0
- Tags:
- Time Limit: {'seconds': 2, 'nanos': 0} seconds
- Memory Limit: 1073741824 bytes
Task
Solve this competitive programming problem. Provide a complete solution that handles all the given constraints and edge cases.