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