#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(){
  int a,c;
  cin >> a >> c;
  int b = 0;
  while(1){
    if((a^b) == c){
      cout << b << endl;
      break;
    }
    b++;
  }
  return 0;
}