我本可以让你计算反 $K_4$ 子图的数量，但这不过是解决这个问题并抄袭 GP of Nanjing 2021 中的 K 题（https://codeforces.com/gym/103470/problem/K）（ecnerwala 的题解见 https://codeforces.com/blog/entry/97762?#comment-866645），我为什么要这么做呢？
给定一个简单无向图。计算其 $K_4$ 子图的数量（即图中存在 4 个顶点，且这 4 个顶点之间两两相连，共有 6 条边）。
一个简单图。$4 \le n \le 100\,000$，$0 \le m \le 100\,000$。保证没有自环或重边。
本题使用标准校验器。
5 9 1 2 1 3 1 4 1 5 2 3 2 4 2 5 3 4 3 5
2
4 0
0
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