a = input()
b = input()
c = len(a)
d = len(b)
ans = 0
if c<=d:
  a = a.rjust(d,'0')
  a = list(a)
  b = list(b)
  for i in range(1,d+1):
    if a[-1*i]!=b[-1*i]:
      ans+=2**(i-1)
else:
  b = b.rjust(c,'0')
  a = list(a)
  b = list(b)
  for i in range(1,c+1):
    if a[-1*i]!=b[-1*i]:
      ans+=2**(i-1)
print(ans)