#include <bits/stdc++.h>
// #include <atcoder/modint>
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define rep2(i, s, n) for(int i = (s); i < (int)(n); i++)
#define printYN(check) cout << ((check)? "Yes" : "No") << endl
#define NUM 998244353
#define IMAX INT_MAX
#define LMAX LONG_MAX
using namespace std;
// using namespace atcoder;
// using mint = modint998244353;
using vi = vector<int>;
using vvi = vector<vi>;
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using vs = vector<string>;
using vb = vector<bool>;
using vvb = vector<vb>;
using pii = pair<int, int>;
using vpii = vector<pii>;
using tii = tuple<int, int, int>;
using mii = map<int, int>;
using Graph = vvi;
// Graph graph(n);
// vi dx = {-1, 0, 1, -1, 1, -1,  0, 1};
// vi dy = { 1, 1, 1,  0, 0, -1, -1,-1};
// snippet -> {UnionFind, dfs_reculsive, dfs_stack, is_prime, mypow, 
//              bfs_queue, digsum, binary_search, gcd, Dijkstra, bitsearch}
// -------------------------------------------------------------------------

int main() {
    string a, b;
    cin >> a >> b;
    reverse(a.begin(), a.end());
    reverse(b.begin(), b.end());
    // cerr << a << "\n" << b << endl;
    int as = a.size(), bs = b.size();
    string s = "";
    rep(i, max(as, bs)) {
        int j = 0, k = 0;
        if(i < as) {
            j = a[i] - '0';
        }
        if(i < bs) {
            k = b[i] - '0';
        }
        j = j ^ k;
        s.push_back('0' + j);
    }
    // cerr << s << endl;
    ll ans = 0;
    ll x = 1;
    rep(i, s.size()) {
        if(s[i] == '1') {
            ans += x;
        }
        x *= 2;
    }
    cout << ans << endl;
    return 0;
}