문제
**Note: the time limit for this problem is 3s, 50% larger than the default. The memory limit is twice the default.**
There are initially M (1≤M≤2⋅105) pairs of friends among FJ's N (2≤N≤2⋅105) cows labeled 1…N.
The cows are leaving the farm for vacation one by one.
On day i, the i-th cow leaves the farm, and all pairs of the i-th cow's friends still present on the farm become friends. How many new friendships are formed in total?
입력
The first line contains N and M.
The next M lines contain two integers ui and vi denoting that cows ui and vi are friends (1≤ui,vi≤N, ui≠vi). No unordered pair of cows appears more than once.
출력
One line containing the total number of new friendships formed. Do not include pairs of cows that were already friends at the beginning.
예제1
7 6
1 3
1 4
7 1
2 3
2 4
3 5
5