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A15137 | Unique Occurrences

时间限制1s
内存限制256MB
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题目描述

You are given a tree, consisting of $n$ vertices. Each edge has an integer value written on it.

Let $f(v, u)$ be the number of values that appear exactly once on the edges of a simple path between vertices $v$ and $u$ .

Calculate the sum of $f(v, u)$ over all pairs of vertices $v$ and $u$ such that $1 \le v < u \le n$ .

输入格式

The first line contains a single integer $n$ ( $2 \le n \le 5 \cdot 10^5$ ) — the number of vertices in the tree.

Each of the next $n-1$ lines contains three integers $v, u$ and $x$ ( $1 \le v, u, x \le n$ ) — the description of an edge: the vertices it connects and the value written on it.

The given edges form a tree.

输出格式

Print a single integer — the sum of $f(v, u)$ over all pairs of vertices $v$ and $u$ such that $v < u$ .

输入输出样例

输入 #1
3
1 2 1
1 3 2
输出 #1
4
输入 #2
3
1 2 2
1 3 2
输出 #2
2
输入 #3
5
1 4 4
1 2 3
3 4 4
4 5 5
输出 #3
14
输入 #4
2
2 1 1
输出 #4
1
输入 #5
10
10 2 3
3 8 8
4 8 9
5 8 5
3 10 7
7 8 2
5 6 6
9 3 4
1 6 3
输出 #5
120
C++ 编辑器
输入
输出