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