a, c = map(int, input().split())

if a > c:
    a, c = c, a

aa = bin(a) #aを2進数にする(上２つは'0b')
cc = bin(c) #cを2進数にする(上２つは'0b')

# print("a_2 = ",aa)
# print("c_2 = ",cc)

#例)c = 101011, a = 1101 -> b = 100110

al = len(aa)
cl = len(cc)

b = ""
b = b + '0b' 

d = abs(cl - al) 

if d == 0:
    for i in range(2, al):
        if aa[i] == cc[i]:
            if aa[i] == '1':  # cc[i] == 1
                b = b + '0'
            else:             # cc[i] == 0
                b = b + '0'
        else:
            if aa[i] == '1':  # cc[i] == 0
                b = b + '1'
            else:             # cc[i] == 1
                b = b + '1'

elif d != 0:
    for i in range(2, d + 2):
        b = b + str(cc[i])

    for j in range(2, al):
        if aa[j] == cc[j+d]:
            if aa[j] == '1':  # cc[j] = 1
                b = b + '0'  
            else:             # cc[j] = 0
                b = b + '0'
        elif aa[j] != cc[j+d]:
            if aa[j] == '1':  # cc[j] = 0
                b = b + '1'
            else:             # cc[j] = 1
                b = b + '1'


                

        
# print(b)
print(int(b, 2))