class Solution(object):

def addBinary(self, a, b):

"""

:type a: str

:type b: str

:rtype: str

"""

len_a = len(a)

len_b = len(b)

if len_a < len_b:

a = (len_b - len_a)*'0' + a

else:

b = (len_a - len_b)*'0' + b

c = 0

result = ''

for i in range(len(a))[::-1]:

if ord(a[i]) - ord('0') + ord(b[i]) - ord('0') + c == 3:

result = '1' + result

c = 1

elif ord(a[i]) - ord('0') + ord(b[i]) - ord('0') + c == 2:

result = '0' + result

c = 1

else:

result = str(ord(a[i]) - ord('0') + ord(b[i]) - ord('0') + c) + result

c = 0

if c == 1:

result = '1' + result

return result