B. Destruction of a Treetime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputYou 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.InputThe 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.OutputIf 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.ExamplesInput50 1 2 1 2OutputYES12354Input40 1 2 3OutputNONoteIn 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.  
Input50 1 2 1 2
OutputYES12354
['constructive algorithms', 'dfs and similar', 'dp', 'greedy', 'trees', '*2000']