#include<bits/stdc++.h>
//#include"atcoder/all"
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define all(a) (a).begin(),(a).end()
using namespace std;
//using namespace atcoder;
typedef long long ll;
int main(){
  ll a,c;cin >> a >> c;
  cout << (a^c) << "\n";
}