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<bits/stdc++.h>
using namespace std;
const int N=505;
int a[N*N],b[N*N];
int n,m,ans,wei[N];
bitset<N> f[N],tmp;
int main(){
	scanf("%d%d",&n,&m);
	for (int i=1;i<=m;i++)
		scanf("%d%d",&a[i],&b[i]);
	for (int i=1;i<=n;i++){
		tmp.reset(); tmp[i]=1;
		for (int j=m;j;j--)
			if (tmp[a[j]]&tmp[b[j]]){
				wei[i]=1; break;
			}
			else if (tmp[a[j]]|tmp[b[j]])
				tmp[a[j]]=tmp[b[j]]=1;
		f[i]=tmp;
	}
	for (int i=1;i<=n;i++)
		for (int j=i+1;j<=n;j++)
			if (!wei[i]&&!wei[j])
				if (!(f[i]&f[j]).count()) ans++;
	printf("%d",ans);
}