import math
A,B=map(int,input().split())
if A==B==0:
    print(0.25)
else:
    g=math.gcd(A,B)
    X=0
    T=8*(g<=20)+2
    F=(A//g)%2*(B//g)%2+1
    for k in range(0,T):
        h=F*k*g+2
        X+=(F*k+1)/(h**h)
    print(X)