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