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