#include <fstream>

using namespace std;

ifstream cin("trapez.in");
ofstream cout("trapez.out");
int n,a[1001],b[1001],nr;

void citire()
{
  cin>>n;

  for(int i=1;i<=n;++i)
      cin>>a[i]>>b[i];

}

void rezolvare()
{
  bool ord=0;
  int aux;
  while(!ord)
  {
      ord=1;
      for(int i=1;i<n;++i)
      if(a[i]>a[i+1])
      {aux=a[i];
       a[i]=a[i+1];
       a[i+1]=aux;
       ord=0;
      }
  }
  int ct1=0,ct2=0;
  for(int i=2;i<=n;++i)
    if(a[i]==a[i-1])++ct1;
    ord=0;
    while(!ord)
  {
      ord=1;
      for(int i=1;i<n;++i)
      if(b[i]>b[i+1])
      {aux=b[i];
       b[i]=b[i+1];
       b[i+1]=aux;
       ord=0;
      }
  }
  for(int i=2;i<=n;++i)
    if(b[i]==b[i-1])++ct2;

  nr=ct1*(ct1-1)/2+ct2*(ct2-1)/2;
  cout<<nr;
}


int main()
{citire();
 rezolvare();

    return 0;
}