a_raw, b_raw = map(int, input().split())

a = bin(a_raw)[2:]
b = bin(b_raw)[2:]
L = max(len(a), len(b))
a = a.zfill(L)
b = b.zfill(L)

ans = 1
for i in range(L):
    if a[i] == '0' and b[i] == '1':
        ans *= 2
    elif a[i] == '1' and b[i] == '0':
        print(0)
        exit()

if ans == 1:
    print(1)
else:
    print(ans // 2)