func_code_string: #include <bits/stdc++.h>   using namespace std;   void debug() { cout << endl; }   template <typename T, typename... E>   void debug(T t, E... e) {     cout << t << (sizeof...(e) ?     :   );     debug(e...);   }   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     int a, b, c, d;     cin >> a >> b >> c >> d;     double p1 = double(a) / b;     double p2 = double(c) / d;     double ans = p1 / (1 - (1 - p1) * (1 - p2));     cout << ans <<   n ;   }   