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4635：Strongly connected

题目描述
Give a simple directed graph with N nodes and M edges. Please tell me the maximum number of the edges you can add that the graph is still a simple directed graph. Also, after you add these edges, this graph must NOT be strongly connected.
A simple directed graph is a directed graph having no multiple edges or graph loops.
A strongly connected digraph is a directed graph in which it is possible to reach any node starting from any other node by traversing edges in the direction(s) in which they point.
输入解释
The first line of date is an integer T, which is the number of the text cases.
Then T cases follow, each case starts of two numbers N and M, 1<=N<=100000, 1<=M<=100000, representing the number of nodes and the number of edges, then M lines follow. Each line contains two integers x and y, means that there is a edge from x to y.
输出解释
For each case, you should output the maximum number of the edges you can add.
If the original graph is strongly connected, just output -1.
输入样例 
3
3 3
1 2
2 3
3 1
3 3
1 2
2 3
1 3
6 6
1 2
2 3
3 1
4 5
5 6
6 4
输出样例 
Case 1: -1
Case 2: 1
Case 3: 15
来自杭电HDUOJ的附加信息
Recommend zhuyuanchen520
该题目是Virtual Judge题目，来自 杭电HDUOJ
题目来源 2013 Multi-University Training Contest 4
源链接： HDU-4635
最后修改于 2020-10-25T23:15:21+00:00 由爬虫自动更新
共提交 0 次
通过率 --%
时间上限 内存上限
2000/1000MS(Java/Others) 32768/32768K(Java/Others)