#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i< (int)(n); i++)
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
ll INF = 2e18;
#define Yes cout << "Yes" << endl
#define No cout << "No" << endl
#define YN {cout<<"Yes"<<endl;}else{cout<<"No"<<endl;} // true → Yes false → No
// cout << fixed << setprecision(20);

int main() {
    ll a,b; cin>>a>>b;
    for(int i=1; i<10000; i++) {
        ll t = (a^i);
        if(t==b) {
            cout << i << endl;
            return 0;
        }
    }
}