#include <bits/stdc++.h>
using namespace std;
#define rep(i, s, n) for (int i = (s); i < (int)(n); i++)


int main() {
    string s, t; cin >>s >> t;
    if(s > t) swap(s, t);
    while(s.size() < t.size()) {
        s = '0' + s;
    }
    string ans = "";
    rep(i, 0, ans.size()) {
        if(s[i] == '1') {
            if(t[i] == '0') ans += '1';
            else ans += '0';
        } else {
            if(t[i] == '0') ans += '0';
            else ans += '1';
        }
    }
    int z = 0;
    rep(i, 0, ans.size()) {
        z *= 2;
        if(ans[i] == '1') z++;
    }
    cout << z << endl;
}