#include <math.h>
#include <stdio.h>

#define EPS 1e-7

double height(double A,double x,int i)
{
    return (i-1)*x - (i-2)*A - 4*i + 4 + i*i + i - 2;
}

double solve(double A,int N)
{
    double x,upper=A,lower=0;
    while(1) {
        int i;
        if(fabs(upper-lower)<EPS)
            break;
        x=(upper+lower)/2;
        for(i=1; i<=N; i++) {
            if(height(A,x,i)<0) {
                lower=x;
                goto next;
            }
        }
        upper=x;
      next:
        ;
    }
    return height(A,x,N);
}

int main()
{
    double A;
    int N;
    scanf("%d%lf",&N,&A);
    printf("%.2f\n",solve(A,N));
    return 0;
}