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