a = int(input())
b = int(input())
assert 0 <= a <= 1 << 30
assert 0 <= b <= 1 << 30
a = list(map(int, str(a)))
b = list(map(int, str(b)))
assert max(a) == 1
assert max(b) == 1
assert len(a) > 1 and a[0] == 1 or len(a) == 1
assert len(b) > 1 and b[0] == 1 or len(b) == 1
if len(a) > len(b):
  a, b = b, a
res = [0] * 31
for i in range(len(a)):
  res[~i] = a[~i] ^ b[~i]
for i in range(len(a), len(b)):
  res[~i] = b[~i]
ans = 0
for i in range(31):
  ans += res[~i] << i
print(ans)