func_code_string: #include <bits/stdc++.h>   using namespace std;   int n;   double p, e[100010], dp[100010];   int main() {     scanf( %d , &n);     for (int i = 1; i <= n; i++) {       scanf( %lf , &p);       e[i] = p * (e[i - 1] + 1);       dp[i] = dp[i - 1] + (2 * e[i - 1] + 1) * p;     }     printf( %.9lf , dp[n]);   }   