#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, x1, y1, x2, y2, t = 0;
  scanf("%d", &n);
  for (i = 0; i < n; ++i) {
    scanf("%d %d %d %d", &x1, &y1, &x2, &y2);
    t += (x2 - x1 + 1) * (y2 - y1 + 1);
  }
  cout << t << endl;
}
