#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x1, x2, y1, y2, s = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> x1 >> y1 >> x2 >> y2;
    s += (x2 - (x1 - 1)) * (y2 - (y1 - 1));
  }
  cout << s;
}
