def main():
    A, C = map(int, input().split())
    A = format(A, 'b')
    C = format(C, 'b')

    a_length = len(A)
    c_length = len(C)

    if a_length > c_length:
        diff = a_length - c_length
        C = '0' * diff + C
    elif a_length < c_length:
        diff = c_length - a_length
        A = '0' * diff + A

    ans = ''
    list_a = list(A)
    list_c = list(C)
    #print("list_a", list_a)
    #print("list_c", list_c)
    for i in range(len(A)):
        if list_a[i] == list_c[i]:
            ans += '0'
        else:
            ans += '1'
    print(int(ans, 2))


if __name__ == '__main__':
    main()