func_code_string: #include <bits/stdc++.h>   using namespace std;   double a, b, c, d;   int main() {     char st =  e ;     cin >> a >> b >> c >> d;     if (a / b == b / c && b / c == c / d) st =  g ;     if (a - b == b - c && b - c == c - d) st =  a ;     if (st ==  e )       cout << 42 << endl;     else if (st ==  g ) {       int d1 = d, b1 = b, a1 = a;       if (d * b / a == d1 * b1 / a1)         cout << d * b / a << endl;       else         cout << 42 << endl;     } else       cout << d + b - a << endl;   }   