There are N turkeys. We number them from 1 through N.

M men will visit here one by one. The i-th man to visit will take the following action:

* If both turkeys x_i and y_i are alive: selects one of them with equal probability, then eats it.
* If either turkey x_i or y_i is alive (but not both): eats the alive one.
* If neither turkey x_i nor y_i is alive: does nothing.



Find the number of pairs (i,\ j) (1 ≤ i < j ≤ N) such that the following condition is held:

* The probability of both turkeys i and j being alive after all the men took actions, is greater than 0.

Constraints

* 2 ≤ N ≤ 400
* 1 ≤ M ≤ 10^5
* 1 ≤ x_i < y_i ≤ N

Input

Input is given from Standard Input in the following format:


N M
x_1 y_1
x_2 y_2
:
x_M y_M


Output

Print the number of pairs (i,\ j) (1 ≤ i < j ≤ N) such that the condition is held.

Examples

Input

3 1
1 2


Output

2


Input

4 3
1 2
3 4
2 3


Output

1


Input

3 2
1 2
1 2


Output

0


Input

10 10
8 9
2 8
4 6
4 9
7 8
2 8
1 8
3 4
3 4
2 7


Output

5
#include<cstdio>
const int MAXM = 400;
const int MAXN = 100000;
int X[MAXN + 5], Y[MAXN + 5], N, M;
bool vis[MAXM + 5][MAXM + 5], f[MAXM + 5];
void Function(int x) {
	vis[x][x] = f[x] = true;
	for(int i=M;i>=1;i--) {
		if( vis[x][X[i]] && vis[x][Y[i]] ) {
			f[x] = false;
			return ;
		}
		if( vis[x][X[i]] || vis[x][Y[i]] )
			vis[x][X[i]] = vis[x][Y[i]] = true;
	}
}
int main() {
	scanf("%d%d", &N, &M);
	for(int i=1;i<=M;i++)
		scanf("%d%d", &X[i], &Y[i]);
	for(int i=1;i<=N;i++)
		Function(i);
	int ans = 0;
	for(int i=1;i<=N;i++) {
		for(int j=i+1;j<=N;j++) {
			if( (!f[i]) || (!f[j]) ) continue;
			bool flag = true;
			for(int k=1;k<=N;k++) {
				if( vis[i][k] && vis[j][k] ) {
					flag = false;
					break;
				}
			}
			if( flag ) ans++;
		}
	}
	printf("%d\n", ans);
}