#include <iostream>
#include <fstream>
using namespace std;
int wu[2000001], wv[2000001];
int main()
{
    ifstream fin("trapez.in"); ofstream fout("trapez.out");
    int n,i, kv,ku, u[1002],v[1002];
    fin>>n;
    ku=0; kv=0;
    for(i=1;i<=n;i++)
    {
        fin>>u[i]>>v[i];
        wu[u[i]]++; wv[v[i]]++;
        if(wu[u[i]]==2) ku++;
        if(wv[v[i]]==2) kv++;
    }
    fout<<(ku*(ku-1))/2+(kv*(kv-1))/2;
}