#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;

int main(int argc, char *argv[]) { ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
ll a,c;cin>>a>>c;
ll b=(a^c);
cout<<b<<endl;
  return 0;
}