s=input()
t=input()
sn=len(s)
tn=len(t)
sint,tint=0,0
for i in range(sn):
	sint+=int(s[::-1][i])*2**i
	# print(int(s[::-1][i])*2**i)
for i in range(tn):
	tint+=int(t[::-1][i])*2**i
# print(sint,tint)
print(sint^tint)