def main():
    A, B = map(int, input().split())
    if A > B:
        print(0)

    cnt = 1
    for i in range(40):
        if A & (1 << i):
            if B & (1 << i):
                cnt *= 1
            else:
                cnt *= 0
        else:
            if B & (1 << i):
                cnt *= 2
            else:
                cnt *= 1

    if cnt == 1:
        print(cnt)
        exit()
    else:
        print(cnt // 2)



if __name__ == "__main__":
    main()