#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;
using ll = long long;

int main(){

    ll ans = 0, N;
    string A, B;
    cin >> A >> B;
    if (A.size() > B.size()) swap(A, B);
    A = string(B.size()-A.size(), '0') + A;
    N = A.size();
    for (int i=0; i<N; i++){
        if (A[i] != B[i]) ans += 1LL<<(N-1-i);
    }

    cout << ans << endl;

    return 0;
}