a = list(map(int, list(input())))
b = list(map(int, list(input())))

a.reverse()
b.reverse()

m = max(len(a), len(b))
while len(a) < m:
  a.append(0)

while len(b) < m:
  b.append(0)

a.reverse()
b.reverse()

ans = 0
for i in range(m):
  ans |= ((a[i] ^ b[i]) << (m - 1 - i))

print(ans)