func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     double a, b, c, d;     cin >> a >> b >> c >> d;     double mx;     mx = (a / b) * (1 / (1 - (1 - a / b) * (1 - c / d)));     std::cout << std::setprecision(9) << mx <<   n ;   }   