func_code_string: #include <bits/stdc++.h>   double A[200000], B[200000], C[200000], p[200000], F[200000];   int i, j, n, m;   int main() {     scanf( %d , &n);     double now, last = 0;     C[0] = 1;     for (i = 1; i <= n; i++) {       if (i <= n) scanf( %lf , &now);       C[i] = now * (C[i - 1]) + 1 - now;       B[i] = now * (B[i - 1] + C[i - 1]);       A[i] = (A[i - 1] + 2 * B[i - 1] + C[i - 1]) * now + (1 - now) * A[i - 1];       last = now;     }     printf( %.9lf n , A[n]);     return 0;   }   