CF1098A.Sum in the tree

Mitya has a rooted tree with $n$ vertices indexed from $1$ to $n$, where the root has index $1$. Each vertex $v$ initially had an integer number $a_v \ge 0$ written on it. For every vertex $v$ Mitya has computed $s_v$: the sum of all values written on the vertices on the path from vertex $v$ to the root, as well as $h_v$ — the depth of vertex $v$, which denotes the number of vertices on the path from vertex $v$ to the root. Clearly, $s_1=a_1$ and $h_1=1$.

Then Mitya erased all numbers $a_v$, and by accident he also erased all values $s_v$ for vertices with even depth (vertices with even $h_v$). Your task is to restore the values $a_v$ for every vertex, or determine that Mitya made a mistake. In case there are multiple ways to restore the values, you're required to find one which minimizes the total sum of values $a_v$ for all vertices in the tree.

米提亚有一棵以 $1$ 为根的有根树，树上有 $n$ 个顶点，编号从 $1$ 到 $n$。每个顶点 $v$ 最初写有一个整数 $a_v \ge 0$。对于每个顶点 $v$，米提亚计算了 $s_v$：从顶点 $v$ 到根节点路径上所有顶点所写数值之和；以及 $h_v$：顶点 $v$ 的深度，即从顶点 $v$ 到根节点路径上的顶点个数。显然，$s_1 = a_1$ 且 $h_1 = 1$。

随后，米提亚擦除了所有 $a_v$ 的值，并且不小心也擦除了所有偶数深度顶点（即满足 $h_v$ 为偶数的顶点）对应的 $s_v$ 值。你的任务是恢复每个顶点的 $a_v$ 值，或判定米提亚犯了错误。若存在多种恢复方案，你需要找出其中一种使得整棵树上所有顶点的 $a_v$ 值之和最小的方案。

The first line contains one integer $n$ — the number of vertices in the tree ($2 \le n \le 10^5$). The following line contains integers $p_2$, $p_3$, ... $p_n$, where $p_i$ stands for the parent of vertex with index $i$ in the tree ($1 \le p_i \lt i$). The last line contains integer values $s_1$, $s_2$, ..., $s_n$ ($-1 \le s_v \le 10^9$), where erased values are replaced by $-1$.

第一行包含一个整数 $n$ —— 树中顶点的数量（$2 \le n \le 10^5$）。
接下来的一行包含整数 $p_2$, $p_3$, ..., $p_n$，其中 $p_i$ 表示树中编号为 $i$ 的顶点的父节点（$1 \le p_i \lt i$）。
最后一行包含整数值 $s_1$, $s_2$, ..., $s_n$（$-1 \le s_v \le 10^9$），其中被擦除的值用 $-1$ 代替。

Output one integer — the minimum total sum of all values $a_v$ in the original tree, or $-1$ if such tree does not exist.

输出一个整数——原始树中所有值 $a_v$ 的最小总和；如果这样的树不存在，则输出 $-1$。