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<iostream>
#include<cstdio>
using namespace std;
#define MAX 100100
inline int read()
{
	int x=0;bool t=false;char ch=getchar();
	while((ch<'0'||ch>'9')&&ch!='-')ch=getchar();
	if(ch=='-')t=true,ch=getchar();
	while(ch<='9'&&ch>='0')x=x*10+ch-48,ch=getchar();
	return t?-x:x;
}
int ans,n,m,a[MAX],b[MAX];
bool alv[404][404],book[MAX];
int main()
{
	n=read();m=read();
	for(int i=1;i<=m;++i)a[i]=read(),b[i]=read();
	for(int i=1;i<=n;++i)
	{
		alv[i][i]=true;
		for(int j=m;j;--j)
		{
			int u=a[j],v=b[j];
			if(alv[i][u]&&alv[i][v]){book[i]=true;break;}
			if(alv[i][u]||alv[i][v])alv[i][u]=alv[i][v]=true;
		}
	}
	for(int i=1;i<=n;++i)
		for(int j=i+1;j<=n;++j)
		{
			if(book[i]||book[j])continue;
			bool fl=false;
			for(int k=1;k<=n;++k)if(alv[i][k]&&alv[j][k]){fl=true;break;}
			if(!fl)++ans;
		}
	printf("%d\n",ans);
}
