s=input()[::-1]
t=input()[::-1]
ns,nt=len(s),len(t)
ans=""
for i in range(min(ns,nt)):
	ans+=str(int(s[i])^int(t[i]))
# print(ans)
if ns>nt:
	ans+=s[nt:]
else:ans+=t[ns:]
print(int(ans[::-1],2))