s=input()[::-1]
t=input()[::-1]

if len(s)>len(t):
    t+="0"*(len(s)-len(t))
if len(s)<len(t):
    s+="0"*(len(t)-len(s))

ans=""
for i in range(len(s)):
    if s[i]=="0":
        if t[i]=="1":
            ans+="1"
        else:
            ans+="0"
    else:
        if t[i]=="1":
            ans+="0"
        else:
            ans+="1"


a=0

for i in range(len(s)):
    a+=int(ans[i])*pow(2,i)
print(a)