import math as m
n=int(input())
x=float(input())
if n>0:
    s=0
    im=0
    for i in range(1,n+1):
        br=m.factorial(2*i)+x**(2*i)
        im=im+2*i-1
        s+=br/im
    print("%.3f" %s)
elif n==0:
    s=max(m.sin(m.pi*x),m.cos(m.pi/4*x))
    print("%.3f" %s)
else:
    if x!=2:
        s=m.sqrt((n**4+4*x**4)/abs(x-2))
        print("%.3f" %s)
    else:
        print("NEDEFINISANO")