#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
typedef long long ll;
typedef pair<ll,ll> P;
//typedef modint998244353 mint;
int main(void){
    cin.tie(0);
    ios::sync_with_stdio(0);
    ll a,c;
    cin>>a>>c;
    ll b=a^c;
    cout<<b<<endl;

}