#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<utility>
#define REP(i,n) for(int i = 0;i < (n);i++)
#define pb push_back
using namespace std;
const int INF = 1e9;
typedef long long ll;

int main(){
  ll a,c;
  cin >> a >> c;
  ll b = a^c;
  cout << b << endl;
  return 0;
}