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Bobo 有一颗 $n$ 个点的树，点的编号是 $1, 2, \dots, n$. 树有 $(n - 1)$ 条边，第 $i$ 条边的端点是 $a_i$ 和 $b_i$，权值是 $c_i$. 求满足 $u < v$ 的 $(u, v)$ 数量，满足点 $u$ 到点 $v$ 路径上的权值和是 $2019$ 的倍数。
输入文件包含多组数据，请处理到文件结束。
每组数据的第一行包含一个整数 $n$.
接下来 $(n - 1)$ 行，其中第 $i$ 行包含三个整数 $a_i$, $b_i$ 和 $c_i$.
对于每组数据，输出一个整数，表示所求的值。
4 1 2 1 1 3 2018 1 4 1 4 1 2 0 1 3 0 1 4 0 3 1 2 1 2 3 1
2 6 0
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