func_code_string: #include <bits/stdc++.h>   using namespace std;   long long re() {     long long x;     scanf( %lld , &x);     return x;   }   int main() {     long long y1 = re(), x1 = re(), y2 = re(), x2 = re();     long long h = (x2 - x1) / 2 + 1;     cout << h * (((y2 - y1 + 1) + 1) / 2) + (h - 1) * ((y2 - y1 + 1) / 2) << endl;   }   