#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= (n); ++i)
#define rrep(i, n) for (ll i = n; i > 0; --i)
#define bitrep(i, n) for (ll i = 0; i < (1 << n); ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define yesNo(b) ((b) ? "Yes" : "No")
using ll = long long;
using ull = unsigned long long;
using ld = long double;
string alphabet = "abcdefghijklmnopqrstuvwxyz";
string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const double pi = 3.141592653589793;
ll smallMOD = 998244353;
ll bigMOD = 1000000007;

// 2進数から10進数への変換
ll toDecimal(string s)
{
    ll res = 0;
    ll n = s.size();
    rep(i, n)
    {
        res += (s[i] - '0') * (1 << (n - i - 1));
    }
    return res;
}

int main()
{
    string a, b;
    cin >> a >> b;
    cout << (toDecimal(a) ^ toDecimal(b)) << endl;
    return 0;
}