CF963B.Destruction of a Tree

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.

给你一棵树（一个包含 $n$ 个顶点和 $n-1$ 条边的图，且图中任意两个顶点之间均可仅通过其边相互到达）。

若一个顶点的度数为偶数，则该顶点可以被销毁。当你销毁一个顶点时，所有与之相连的边也会一并被删除。

请销毁给定树中的所有顶点，或判断这是不可能的。

The first line contains integer n (1 ≤ n ≤ 2·105) — number of vertices in a tree.

The second line contains n integers _p_1, _p_2, ..., p__n (0 ≤ p__i ≤ n). If p__i ≠ 0 there is an edge between vertices i and p__i. It is guaranteed that the given graph is a tree.

第一行包含一个整数 $n$（$1 \leq n \leq 2 \cdot 10^5$）——树中顶点的数量。

第二行包含 $n$ 个整数 $p_1,\,p_2,\,\dots,\,p_n$（$0 \leq p_i \leq n$）。若 $p_i \neq 0$，则在顶点 $i$ 与 $p_i$ 之间存在一条边。保证所给图是一棵树。

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.

如果可以摧毁所有顶点，则输出 "YES"（不带引号），否则输出 "NO"（不带引号）。

如果可以摧毁所有顶点，则在接下来的 n 行中，按摧毁顺序输出各顶点的编号。若存在多个正确答案，输出任意一个即可。

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.

在第一个示例中，首先需要删除索引为 1 的顶点（此后，边 (1, 2) 和 (1, 4) 被移除），然后删除索引为 2 的顶点（边 (2, 3) 和 (2, 5) 被移除）。此后树中不再含有任何边，因此剩余的顶点可以按任意顺序删除。