#include <bits/stdc++.h>
using namespace std;
int n;
double a[10005];
double l=1,r;
double f(double x)
{
	double t=n,sum=1;
	while(t--)
	{
		sum+=pow(x,t)*double(a[n-int(t)+1]);
	}
	return sum;
}
int main()
{
	cin>>n>>l>>r;
	for (int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	while (r-l>0.00001)
	{
		double tl,tr;
		tl=tl+(tr-tl)/3.0;
		tr=tr-(tr-tl)/3.0;
		if (f(tl)>f(tr))l=tl;
		else r=tr;
	}
	printf("%.5lf",f(l));
	return 0;
}