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

int main() {
    string a, b;
    cin >> a >> b;
    reverse(a.begin(), a.end());
    reverse(b.begin(), b.end());
    if (a.size() > b.size()) {
        swap(a, b);
    }
    string ans = b;
    for (int i = 0; i < a.size(); i++) {
        if (a[i] == '1' && b[i] == '1') {
            ans[i] = '0';
        }
        else if (a[i] == '0' && b[i] == '0') {
            ans[i] = '0';
        }
        else {
            ans[i] = '1';
        }
    }
    int final_ans = 0, k = 1;
    for (auto c : ans) {
        final_ans += k * (c - '0');
        k *= 2;
    }
    cout << final_ans << endl;
}