#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
using namespace std;
using ll = long long;
const int INF = 1000000000;
const int MOD = 1000000007;
const ll llINF = 1000000000000000000;

// #include <atcoder/all>
// using namespace atcoder;
// #include <boost/multiprecision/cpp_int.hpp>
// using lll = boost::multiprecision::cpp_int;
// {{oya, dep}, {ko, ko, ko, ...}}
void solve() {
  int a, b;
  cin >> a >> b;
  cout << (a | b) - (a & b) << endl;
}

int main() {
  std::cin.tie(nullptr);
  std::ios_base::sync_with_stdio(false);
  std::cout << std::fixed << std::setprecision(15);
  solve();
  return 0;
}