#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll inf=20000000000000;
ll mod=998244353;
int main(){
    string a,b;
    cin >> a >> b;
    if (a.size()<b.size())
    {
        reverse(a.begin(),a.end());
        while (a.size()!=b.size())
        {
            a.push_back('0');
        }
        reverse(a.begin(),a.end());
    }else{
        reverse(b.begin(),b.end());
        while (a.size()!=b.size())
        {
            b.push_back('0');
        }
        reverse(b.begin(),b.end());
    }
    for (ll i = 0; i < a.size(); i++)
    {
        if (a[i]=='0'&&b[i]=='1')
        {
            a[i]='1';
        }else if (a[i]=='1'&&b[i]=='1')
        {
            a[i]='0';
        }
    }
    reverse(a.begin(),a.end());
    ll now=1;
    ll ans=0;
    for (ll i = 0; i < a.size(); i++)
    {
        if (a[i]=='1')
        {
            ans+=now;
        }
        now*=2;
    }
    cout << ans << endl;
}