a = input()
b = input()
c = ""
s = 0
for i in range(min(len(a),len(b))):
	if a[-i-1] != b[-i-1]:
		c = "1" + c
	else:
		c = "0" + c
if len(a) > len(b):
	c = a[:len(a)-len(b)] + c
elif len(a) < len(b):
	c = b[:len(b)-len(a)] + c
for i in range(len(c)):
	if c[-i-1] == 1:
		s += 2**i
print(s)