#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
const double esp=1e-6;
int n;
int a[30];
double fen(double x)
{
	double s=0;
	for(int i=n;i>=0;i--)s+=a[i]*pow(x,i);
	return s;
}
int main()
{
	freopen("P3382_1.in","r",stdin);
	double l,r;
	cin>>n>>l>>r;
	fclose(stdin);
	for(int i=n;i>=0;i--)cin>>a[i];
	while(fabs(l-r)>esp)
	{
		double mid=(l+r)/2;
		if(fen(mid+esp)>fen(mid-esp))l=mid;
		else r=mid;
	}
	printf("%.5f",r);
	return 0;
}