#include <stdio.h>

int m,n,a[4100][4100],nr=0;

int main()
{int i,j,k;
FILE *f;
f=fopen("triplete.in","r");
fscanf(f,"%d %d",&m,&n);
for (k=1;k<=n;k++)
    {fscanf(f,"%d %d",&i,&j);
    a[i][j]=1;
    }
fclose(f);

for (i=2;i<=m;i++)
    for (j=i+1;j<=m;j++)
        if (a[i][j]==1)
            if ((a[i-1][j-1]==1)&&(a[i-1][j]==1))
               nr++;
        
FILE *g;
g=fopen("triplete.out","w");
fprintf(g,"%d",nr);
fclose(g);
return 0;
    }