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给定一颗 $n$ 个结点的树，每条边上有一个小写字母。
令 $str(x,y)$ 表示树上 $x$ 到 $y$ 的简单路径上的字母连成的字符串。
定义一个字符串 $T$ 是优秀的，当且仅当 $T$ 能表示成 $SS$ 的形式，其中 $S$ 是一个任意非空字符串。
求树上有多少个本质不同的优秀字符串。
输入第一行一个正整数 $n$（$2 \leq n \leq 5 \times 10^4$），表示树的大小。
接下来 $n-1$ 行，每行形如 $x,y,c$ 表示有一条连接 $(x,y)$ 的边，上面的小写字母是 $c$。
输出一个非负整数表示答案
5 1 2 a 2 3 a 3 4 b 4 5 b
2
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