#include <bits/stdc++.h>
using namespace std;
int a[2005], b[2005];
int main() {
  int n, i, j, x, y, k;
  long long s;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> x >> y;
    a[x + y]++;
    b[1001 + x - y]++;
  }
  s = 0;
  for (i = 0; i < 2003; i++) {
    k = a[i];
    s += (k - 1) * k / 2;
    k = b[i];
    s += (k - 1) * k / 2;
  }
  cout << s << endl;
  return 0;
}
