# 2020/01/02

a,b=map(int,input().split())
bit=bin(a&b).count('0')-1
n=max(len(bin(a))-2,len(bin(b))-2)
aa=bin(a)[2:].zfill(n)
bb=bin(b)[2:].zfill(n)
for ax,bx in zip(aa,bb):
    if int(ax) and not int(bx):
        print(0)
        exit()
print(pow(2,bit-1))