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2868：Neighbor Friend

题目描述
Suppose we sort N persons in a line according to their heights,we are curious about the Neighbor Friend.
A pair of Neighbor Friend is two person next to each other in the line,ignoring the order(ie (x,y) and (y,x)is the same).
Now you are given M pieces of infomation,each with two integer a and b,discribing that person a is shorter than person b.
Can you find how many different pairs of Neighbor Friend that could occur in some of the sorted line?
输入解释
Input contains multiple cases.
Each test case starts with two integer N(2<=N<=200) ,M(0<=M<1000) ,indicating that there are N persons and M pieces of information.Follow by M lines,each line contains two integers a and b,represents that person a is shorter than person b.
输出解释
For each test case, output the different pairs of Neighbor Friend that could occur in some of the sorted line.
输入样例 
3 1
1 2
3 2
1 2
2 3
输出样例 
3
2
提示

Hint
In sample 1,we know that person 1 is shorter than person 2, there may be three kind of sorted results: 3 1 2,1 3 2,1 2 3.(1,3),(1,2) and (2,3) could be found among them.
In sample 2,we know that person 1 is shorter than person 2,and person 2 is shorter than person 3,so there is only one kind of sorted results:1 2 3.We can’t find (1,3),so
the answer is 2.
来自杭电HDUOJ的附加信息
Recommend gaojie
该题目是Virtual Judge题目，来自 杭电HDUOJ
题目来源 2009 Multi-University Training Contest 7 - Host by FZU
源链接： HDU-2868
最后修改于 2020-10-25T22:57:40+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)