def trfm(x):
    r = []
    while x > 0:
        r += [x % 2]
        x = x // 2
    return r


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

ta = trfm(a)
tc = trfm(c)
while len(ta) != len(tc):
    if len(ta) < len(tc):
        ta.append(0)
    else:
        tc.append(0)

tb = []
for i in range(len(tc)):
    tb.append(abs(tc[i] - ta[i]))

ans = 0
for i in range(len(tb)):
    ans += tb[i] * (2 ** i)
print(ans)