func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<int> a;   int x;   int main() {     while (cin >> x) {       a.push_back(x);     }     if (((a[3] - a[2]) == (a[2] - a[1])) && ((a[2] - a[1]) == (a[1] - a[0]))) {       cout << a[3] + a[3] - a[2] << endl;       return 0;     } else {       if (a[0] != 0) {         if (a[1] != 0) {           if (a[1] != a[0]) {             if ((((double)a[1] / a[0]) == ((double)a[2] / a[1])) &&                 (((double)a[2] / a[1]) == ((double)a[3] / a[2]))) {               if ((int)(a[3] * ((double)a[3] / a[2])) ==                   (a[3] * ((double)a[3] / a[2]))) {                 cout << a[3] * ((double)a[3] / a[2]) << endl;                 return 0;               }             }           }         }       }     }     cout << 42 << endl;     return 0;   }   