// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
int main() {
    // Input
    string A, B;
    cin >> A >> B;

    // Calculation
    reverse(A.begin(), A.end());
    reverse(B.begin(), B.end());
    string C;
    for (int i = 0; ; ++i) {
        if (i < A.size() && i < B.size()) C += (A[i] == B[i] ? '0' : '1');
        else if (i < A.size()) C += A[i];
        else if (i < B.size()) C += B[i];
        else break;
    }

    // Output
    int ans = 0;
    for (int i = 0, p = 1; i < C.size(); ++i, p <<= 1) ans += p * (C[i] == '1');
    cout << ans << endl;
}