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