#include <iostream>
#include <iomanip>
#include <cmath>

#define EPSILON (1e-12)

#define LT(x,y) (((x)-(y)) <  -EPSILON)
#define LE(x,y) (((x)-(y)) <= +EPSILON)

using namespace std;

double Hmin(double H1, double H2)
{
	double axis = (H1 - H2 + 3.0) / 2.0;

	double a = floor(axis + EPSILON);
	double b = ceil(axis - EPSILON);

	double Ha = (a - 2) * (a - 1) + (a - 1) * H2 - (a - 2) * H1;
	double Hb = (b - 2) * (b - 1) + (b - 1) * H2 - (b - 2) * H1;
	return (Ha < Hb) ? Ha : Hb;
}

double compute(double N, double H1)
{
	double H2min = ((N-2) * H1 - (N-1) * (N-2)) / (N-1) - EPSILON;
	double H2max = H1 - 1.0;
	double H2;

	// Can H[N] get 0.0?
	double axis = (H1 - H2min + 3.0) / 2.0;
	if(LE(N, axis)) return 0.0;

	// Compute by iteration
	while(LT(H2min, H2max)) {
		H2 = (H2min + H2max) / 2.0;
		if(Hmin(H1, H2) < 0.0) H2min = H2; else H2max = H2;
	}

	H2 = (H2min + H2max) / 2.0;
	return (N-2) * (N-1) + (N-1) * H2 - (N-2) * H1;
}

int main(void)
{
	double N, A;
	cin >> N >> A;
	cout << setprecision(2) << fixed << compute(N, A) << endl;
	return 0;
}