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