#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int ans = 0;
  for (int i = 0; i < n; ++i) {
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    int T = (c - a + 1) * (d - b + 1);
    ans += T;
  }
  cout << ans << "\n";
  return 0;
}
