#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    string s, t;
    cin >> s >> t;
    ll a = 0, b = 0;
    reverse(s.begin(), s.end());
    reverse(t.begin(), t.end());
    for(int i = 0; i < s.size(); i++){
        if(s[i] == '1') a |= 1ll << i;
    }
    for(int i = 0; i < t.size(); i++){
        if(t[i] == '1') b |= 1ll << i;
    }
    cout << (a ^ b) << '\n';
}