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 maxn=400+10,maxm=1e5+10;
int n,m,x[maxm],y[maxm];
bool ok[maxn],S[maxn][maxn];
bool check(int i,int j)
{
	for (int k=1;k<=n;k++)
	    if (S[i][k]&&S[j][k])
	        return 0;
	return 1;
}
int main()
{
	cin>>n>>m;
	for (int i=1;i<=m;i++) scanf("%d%d",&x[i],&y[i]);
	for (int i=1;i<=n;i++)
	{
	    ok[i]=1;
	    S[i][i]=1;
		for (int j=m;j>=1;j--)
		{
		    if (S[i][x[j]]&&S[i][y[j]])
		    {
		    	ok[i]=0;break;
			}
			if (S[i][x[j]]&&!S[i][y[j]])
			    S[i][y[j]]=1;
			if (!S[i][x[j]]&&S[i][y[j]])
			    S[i][x[j]]=1;
		}
	}
	int ans=0;
	for (int i=1;i<=n;i++)
	    for (int j=i+1;j<=n;j++)
	        if (ok[i]&&ok[j]&&check(i,j))
	            ans++;
	cout<<ans;
	return 0;
}