func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = -1;   const long long INF = 1e9 + 19;   int main() {     int n, m, x;     scanf( %d%d%d , &n, &m, &x);     x--;     auto f = [&](int y) {       int nn = n - y * 2;       int mm = m - y * 2;       if (nn <= 0 || mm <= 0) {         return 0;       }       return (nn * mm + 1) / 2;     };     cout << f(x) - f(x + 1) << endl;     return 0;   }   