#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
using ll = long long;
const ll MOD = 998244353;


int main() {
    int x,y,ans;
    cin >> x >> y;
    for (int i =0; i<256;i++){
        if ((x ^ i) == y) {
            ans=i;
        }
    }
    cout << ans << endl;
}