CF1143C.Queen

You are given a rooted tree with vertices numerated from $1$ to $n$. A tree is a connected graph without cycles. A rooted tree has a special vertex named root.

Ancestors of the vertex $i$ are all vertices on the path from the root to the vertex $i$, except the vertex $i$ itself. The parent of the vertex $i$ is the nearest to the vertex $i$ ancestor of $i$. Each vertex is a child of its parent. In the given tree the parent of the vertex $i$ is the vertex $p_i$. For the root, the value $p_i$ is $-1$.

An example of a tree with $n=8$, the root is vertex $5$. The parent of the vertex $2$ is vertex $3$, the parent of the vertex $1$ is vertex $5$. The ancestors of the vertex $6$ are vertices $4$ and $5$, the ancestors of the vertex $7$ are vertices $8$, $3$ and $5$

You noticed that some vertices do not respect others. In particular, if $c_i = 1$, then the vertex $i$ does not respect any of its ancestors, and if $c_i = 0$, it respects all of them.

You decided to delete vertices from the tree one by one. On each step you select such a non-root vertex that it does not respect its parent and none of its children respects it. If there are several such vertices, you select the one with the smallest number. When you delete this vertex $v$, all children of $v$ become connected with the parent of $v$.

An example of deletion of the vertex $7$.

Once there are no vertices matching the criteria for deletion, you stop the process. Print the order in which you will delete the vertices. Note that this order is unique.

你被给定一棵以 $1$ 到 $n$ 编号的顶点构成的有根树。树是一种无环连通图。有根树中有一个特殊的顶点，称为根（root）。

顶点 $i$ 的祖先（ancestors）是指从根到顶点 $i$ 的路径上除 $i$ 本身外的所有顶点。顶点 $i$ 的父节点（parent）是离 $i$ 最近的祖先。每个顶点都是其父节点的一个子节点（child）。在本题所给的树中，顶点 $i$ 的父节点为顶点 $p_i$；对于根节点，$p_i = -1$。

一棵 $n = 8$ 的树示例，根为顶点 $5$。顶点 $2$ 的父节点是顶点 $3$，顶点 $1$ 的父节点是顶点 $5$。顶点 $6$ 的祖先为顶点 $4$ 和 $5$；顶点 $7$ 的祖先为顶点 $8$、$3$ 和 $5$。

你注意到某些顶点不尊重其他顶点。具体地，若 $c_i = 1$，则顶点 $i$ 不尊重它的任意一个祖先；若 $c_i = 0$，则它尊重所有祖先。

你决定逐个删除树中的顶点。每一步中，你选择一个满足如下条件的非根顶点：它不尊重其父节点，且它的任意一个子节点都不尊重它。若存在多个满足条件的顶点，则选择编号最小的那个。当你删除该顶点 $v$ 时，$v$ 的所有子节点将直接连接至 $v$ 的父节点。

删除顶点 $7$ 的示例。

当不再存在满足删除条件的顶点时，该过程停止。请输出顶点被删除的顺序。注意，该顺序是唯一的。

The first line contains a single integer $n$ ($1 \le n \le 10^5$) — the number of vertices in the tree.

The next $n$ lines describe the tree: the $i$-th line contains two integers $p_i$ and $c_i$ ($1 \le p_i \le n$, $0 \le c_i \le 1$), where $p_i$ is the parent of the vertex $i$, and $c_i = 0$, if the vertex $i$ respects its parents, and $c_i = 1$, if the vertex $i$ does not respect any of its parents. The root of the tree has $-1$ instead of the parent index, also, $c_i=0$ for the root. It is guaranteed that the values $p_i$ define a rooted tree with $n$ vertices.

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

接下来的 $n$ 行描述该树：第 $i$ 行包含两个整数 $p_i$ 和 $c_i$（$1 \le p_i \le n$，$0 \le c_i \le 1$），其中 $p_i$ 是顶点 $i$ 的父节点，而 $c_i = 0$ 表示顶点 $i$ 尊重其父节点，$c_i = 1$ 表示顶点 $i$ 不尊重其任意父节点。树的根节点的父节点索引为 $-1$，且根节点满足 $c_i = 0$。保证所有 $p_i$ 的值构成一棵含 $n$ 个顶点的有根树。

In case there is at least one vertex to delete, print the only line containing the indices of the vertices you will delete in the order you delete them. Otherwise print a single integer $-1$.

如果至少存在一个需要删除的顶点，则输出一行，包含按删除顺序排列的待删除顶点的下标；否则输出单个整数 $-1$。

The deletion process in the first example is as follows (see the picture below, the vertices with $c_i=1$ are in yellow):

• first you will delete the vertex $1$, because it does not respect ancestors and all its children (the vertex $2$) do not respect it, and $1$ is the smallest index among such vertices;
• the vertex $2$ will be connected with the vertex $3$ after deletion;
• then you will delete the vertex $2$, because it does not respect ancestors and all its children (the only vertex $4$) do not respect it;
• the vertex $4$ will be connected with the vertex $3$;
• then you will delete the vertex $4$, because it does not respect ancestors and all its children (there are none) do not respect it (vacuous truth);
• you will just delete the vertex $4$;
• there are no more vertices to delete.

In the second example you don't need to delete any vertex:

• vertices $2$ and $3$ have children that respect them;
• vertices $4$ and $5$ respect ancestors.

In the third example the tree will change this way:

第一个示例中的删除过程如下（见下图，满足 $c_i=1$ 的顶点用黄色标出）：

• 首先删除顶点 $1$，因为它不被其祖先尊重，且其所有子节点（即顶点 $2$）均不尊重它，同时 $1$ 是满足该条件的编号最小的顶点；
• 删除后，顶点 $2$ 将与顶点 $3$ 相连；
• 接着删除顶点 $2$，因为它不被其祖先尊重，且其所有子节点（仅顶点 $4$）均不尊重它；
• 删除后，顶点 $4$ 将与顶点 $3$ 相连；
• 然后删除顶点 $4$，因为它不被其祖先尊重，且其所有子节点（不存在）均不尊重它（空真）；
• 于是直接删除顶点 $4$；
• 此时已无更多顶点可删除。

在第二个示例中，无需删除任何顶点：

• 顶点 $2$ 和 $3$ 均拥有尊重它们的子节点；
• 顶点 $4$ 和 $5$ 均尊重其祖先。

在第三个示例中，树将按如下方式变化：