File size: 1,777 Bytes
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## Problem Description
You are given a tree (a graph with n vertices and n - 1 edges in which it's possible to reach any vertex from any other vertex using only its edges).
A vertex can be destroyed if this vertex has even degree. If you destroy a vertex, all edges connected to it are also deleted.
Destroy all vertices in the given tree or determine that it is impossible.
Input
The first line contains integer n (1 ≤ n ≤ 2·105) — number of vertices in a tree.
The second line contains n integers p1, p2, ..., pn (0 ≤ pi ≤ n). If pi ≠ 0 there is an edge between vertices i and pi. It is guaranteed that the given graph is a tree.
Output
If it's possible to destroy all vertices, print "YES" (without quotes), otherwise print "NO" (without quotes).
If it's possible to destroy all vertices, in the next n lines print the indices of the vertices in order you destroy them. If there are multiple correct answers, print any.
Examples
Input
5
0 1 2 1 2
Output
YES
1
2
3
5
4
Input
4
0 1 2 3
Output
NO
Note
In the first example at first you have to remove the vertex with index 1 (after that, the edges (1, 2) and (1, 4) are removed), then the vertex with index 2 (and edges (2, 3) and (2, 5) are removed). After that there are no edges in the tree, so you can remove remaining vertices in any order.
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## Contest Information
- **Contest ID**: 963
- **Problem Index**: B
- **Points**: 1000.0
- **Rating**: 2000
- **Tags**: constructive algorithms, dfs and similar, dp, greedy, trees
- **Time Limit**: {'seconds': 1, 'nanos': 0} seconds
- **Memory Limit**: 256000000 bytes
## Task
Solve this competitive programming problem. Provide a complete solution that handles all the given constraints and edge cases. |