func_code_string: #include <bits/stdc++.h>   using namespace std;   double p1, p2;   double fastPow(double b, int n) {     if (n == 0) return 1.0;     double po = fastPow(b, n / 2);     po = po * po;     if (n & 1) return po * b;     return po;   }   double proba(int turno) {     double ans = 1;     ans = ans * fastPow(1 - p1, turno / 2);     ans = ans * fastPow(1 - p2, turno / 2);     return ans * p1;     return ans * p1;   }   int main() {     double a, b, c, d;     while (cin >> a >> b >> c >> d) {       double prob = 0;       p1 = a / b;       p2 = c / d;       for (int i = 1; i < 100000; i += 2) prob = prob + proba(i);       cout << prob << endl;     }   }   