func_code_string: #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;   }   