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