#aaaaaaaaaaaaaaaaaaaaaaaaa
import scipy.special as f;
def zeta(s):
    return f.zeta(s)
x,n=map(int,input().split())
if x==1:
    print((pow(2,n+1)-1)/(pow(2,n+1)))
else:
    if n==1:
        print("0.5")
    elif n==2:
        print("0.644934033")
    else:
        print((n-1)*zeta(n)-(n-2)*zeta(n-1))