#include <fstream>
#include <algorithm>

using namespace std;

ifstream fin("trapez.in");
ofstream fout("trapez.out");

int N;
int nrX, nrY;
int xs[1005], ys[1005];

int main()
{
    fin >> N;

    for(int i = 1; i <= N; i++)
        fin >> xs[i] >> ys[i];

    sort(xs + 1, xs + N + 1);
    sort(ys + 1, ys + N + 1);

    for(int i = 2; i < N; i++)
        if(xs[i] == xs[i - 1])
            nrX++;

    for(int i = 2; i < N; i++)
        if(ys[i] == ys[i - 1])
            nrY++;

    int ans = nrX * (nrX - 1) / 2 + nrY * (nrY - 1) / 2;
    fout << ans;

    return 0;
}