#include<iostream>
#include<cstdio>
using namespace std;
#define inf 0x3f3f3f3f
#define maxn 1006
#define eps 1e-8
int n;
double A,num[maxn];
bool solve(double mid)
{
    num[1]=mid;
    for(int i=2;i<n;i++)
	{
        num[i]=2*num[i-1]+2-num[i-2];
        if(num[i]<eps) return false; //写小于0由于精度问题会wa
    }
    return true;
}
int main()
{
    while(cin>>n>>A)
	{
        num[0]=A;
        double low=-inf;
        double high=inf;
        for(int i=0;i<100;i++)
		{
            double mid=(low+high)/2;
            if(solve(mid)) 
				high=mid;
            else
				low=mid;
        }
        printf("%.2lf\n",num[n-1]);
    }
    return 0;
}