//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const double pi = 3.14159265359879323846264338327950288419;
const int INF = 2147483647;
using p = pair<long long, long long>;

int main() {
  bitset<30> a, b;
  cin >> a >> b;
  auto tmp = a^b;
  ll now = 1, ans = 0;
  for(int i = 0; i < 30; i++){
    if(tmp.test(i)) ans += now;
    now *= 2;
  }
  
  cout << ans << endl;
  
}