Tiang Pemancar

#include <cstdio>
#include <cmath>
#include <cstdlib>
using namespace std;
#define R(i,_a,_b) for(int i=int(_a);i<int(_b);i++)

long long hasil;
int n, num1, num2;
int a[510000], b[510000], nx[10000], ny[10000];

int main() {
    scanf("%d", &n);

    R(i,0,n) {
        scanf("%d%d", &a[i], &b[i]);
        nx[ a[i] ]++; ny[ b[i] ]++;
    }

    R(i,0,n) {
        hasil = hasil + (nx[ a[i] ]-1) * (ny[ b[i] ]-1);
    }

    printf("%lld\n", hasil);

    //scanf("\n");
    return 0;
}