func_code_string: #include <bits/stdc++.h>   using namespace std;   double A[200009];   double B[200009];   int main() {     int N, i;     cin >> N;     for (i = 0; i < N; i++) {       cin >> A[i];     }     B[0] = A[0];     for (i = 1; i < N; i++) {       B[i] = (B[i - 1] + 1) * A[i];     }     double sum = 0;     for (i = 0; i < N; i++) {       sum += 2 * B[i];       sum -= A[i];     }     printf( %0.15lf n , sum);     return 0;   }   