#include <iostream>
#include <fstream>
using namespace std;
ifstream f("trapez.in");ofstream g("trapez.out");

int x[1001],y[1001];
int n,i,j,nr,k;

int main()
{f>>n;
for(i=1;i<=n;i++)
    f>>x[i]>>y[i];
for(i=1;i<=n-2;i++)
   for(j=i+1;j<=n-1;j++)
     for(k=j+1;k<=n;k++)
       if((x[i]==x[j] || y[i]==y[j]) && (x[i]==x[k] || y[i]==y[k]))nr++;

g<<nr;
f.close();g.close();
}