#include<bits/stdc++.h>
using namespace std;
int n;
double p,ans[3];
signed main()
{
//	freopen("P1654_1.in","r",stdin);
	cin>>n;
	while(n--)
	{
		cin>>p;
		ans[3]=ans[3]+(3*ans[2]+3*ans[1]+1)*p;
		ans[2]=(ans[2]+2*ans[1]+1)*p;
		ans[1]=(ans[1]+1)*p;
	}
	printf("%.1lf",ans[3]);
	return 0;
}

#1
In

9
0.156
0.731
0.76
0.652
0.134
0.596
0.028
0.714
0.814

Right Out

27.5

My Out

27.5