CF1156D.0-1-Tree

You are given a tree (an undirected connected acyclic graph) consisting of $n$ vertices and $n - 1$ edges. A number is written on each edge, each number is either $0$ (let's call such edges $0$-edges) or $1$ (those are $1$-edges).

Let's call an ordered pair of vertices $(x, y)$ ($x \ne y$) valid if, while traversing the simple path from $x$ to $y$, we never go through a $0$-edge after going through a $1$-edge. Your task is to calculate the number of valid pairs in the tree.

给你一棵树（即一个无向、连通、无环的图），该树包含 $n$ 个顶点和 $n - 1$ 条边。每条边上写有一个数字，该数字非 $0$ 即 $1$（我们将标有 $0$ 的边称为 $0$-边，标有 $1$ 的边称为 $1$-边）。

我们称一个有序顶点对 $(x, y)$（其中 $x \ne y$）是合法的，当且仅当：在从 $x$ 到 $y$ 的唯一简单路径上，不会在经过一条 $1$-边之后再经过一条 $0$-边。你的任务是计算这棵树中合法顶点对的总数。

The first line contains one integer $n$ ($2 \le n \le 200000$) — the number of vertices in the tree.

Then $n - 1$ lines follow, each denoting an edge of the tree. Each edge is represented by three integers $x_i$, $y_i$ and $c_i$ ($1 \le x_i, y_i \le n$, $0 \le c_i \le 1$, $x_i \ne y_i$) — the vertices connected by this edge and the number written on it, respectively.

It is guaranteed that the given edges form a tree.

第一行包含一个整数 $n$（$2 \le n \le 200000$）——树中顶点的数量。

接下来是 $n - 1$ 行，每行表示树中的一条边。每条边由三个整数 $x_i$、$y_i$ 和 $c_i$（$1 \le x_i, y_i \le n$，$0 \le c_i \le 1$，$x_i \ne y_i$）表示——分别为该边所连接的两个顶点以及写在该边上的数字。

保证所给的边构成一棵树。

Print one integer — the number of valid pairs of vertices.

输出一个整数——有效顶点对的数量。

The picture corresponding to the first example:

第一个示例对应的图片：