//#pragma GCC optimize ("O2")
//#pragma GCC optimize ("Ofast")
// IN THE NAME OF GOD
#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;

template<typename Head>
inline void dout(Head in) {
  cerr << in << '\n';
} 

int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  int a, b;
  cin >> a >> b;
  cout << (a | b) - (a & b); 
  return 0;
}