// 32351ZN
#include <iostream>
#include <sstream>
#include <vector>
#include <algorithm>
#include <complex>
#include <list>
#include <cmath>
#include <cfloat>
#include <climits>
#include <cstdlib>

using namespace std;

typedef vector<int> ivec_t;
typedef vector<ivec_t> imat_t;

#define FOR_EACH(p,q,r) for(p=q;p!=r;p++)
#define FOR_EACH_C(p,c) for(p=(c).begin();p!=(c).end();p++)

bool IsNotNegative(double h1, double h2, int n)
{
    double prev_h = h2, prev_prev_h = h1;
    for(int i=2;i<n;i++)
    {
	double h = prev_h * 2 - prev_prev_h + 2;
	// cerr << h << endl;
	if(h < 0) return false;
	prev_prev_h = prev_h;
	prev_h = h;
    }
    return true;
}

double GetB(double h1, double h2, int n)
{
    double prev_h = h2, prev_prev_h = h1;
    double h;
    for(int i=2;i<n;i++)
    {
	h = prev_h * 2 - prev_prev_h + 2;
	// cerr << h << endl;
	//if(h < 0) return false;
	prev_prev_h = prev_h;
	prev_h = h;
    }
    return h;
}

const double ERROR=1e-5;

double Solve(int n, double a)
{
    double high = a, low = 0, mid;
    double prevmid = 0;
    while(1)
    {
	mid = (high + low) / 2;
//	cerr << high << " " << low << " " << mid << endl;
	if(IsNotNegative(a, mid, n))
	{
	    high = mid;
	}
	else
	{
	    low = mid;
	}
	if(abs(high - low) < ERROR) break;
	prevmid = mid;
    }
    return GetB(a, mid, n);
}

int main()
{
    int n;
    double a;
//    cerr << IsNotNegative(15, 8, 8)<< endl;
    cin >> n >> a;
    cout.setf(ios::fixed);
    cout.precision(2);
    cout << Solve(n, a) << endl;
    return 0;
}