## https://yukicoder.me/problems/no/353


def main():
    A, B = map(int, input().split())
    
    a_array = []
    while A > 0:
        a_array.append(A % 2)
        A //= 2

    b_array =[]
    while B > 0:
        b_array.append(B % 2)
        B //=  2

    max_ab_len = max(len(a_array), len(b_array))

    carry_over = 0
    answer = []
    for i in range(max_ab_len):
        a = 0
        if i < len(a_array):
            a = a_array[i]
        b = 0
        if i < len(b_array):
            b = b_array[i]

        if a | b == 0:
            answer.append(carry_over)
            carry_over = 0
        elif a | b == 1 and a & b == 0:
            if carry_over == 0:
                answer.append(a ^ b)
            else:
                answer.append(0)
                carry_over = 1
        elif a & b == 1:
            answer.append(carry_over)
            carry_over = 1

    if carry_over == 1:
        answer.append(carry_over)

    ans = 0
    for a in reversed(answer):
        ans <<= 1
        ans ^= a
    print(ans)






if __name__ == "__main__":
    main()