#include<ext/pb_ds/assoc_container.hpp> 
#include<ext/pb_ds/tree_policy.hpp>
#include<bits/stdc++.h>
#define ll long long
#define pb push_back
using namespace __gnu_pbds;
using namespace std;
typedef tree<string, null_type, less<string>, rb_tree_tag,tree_order_statistics_node_update>
new_data_set;

vector<vector<int>> arr; vector<int> parent,sz ; vector<bool> visited;


int main(){
	ios_base::sync_with_stdio(false);
    cin.tie(NULL); 

    /***********************************/
    
    /*
    int u,v,n,m; cin>>n>>m;
    parent.resize(n); sz.resize(n,1);
    arr.resize(n);  iota(parent.begin(),parent.end(),0); 

    for(int i=0;i<m;i++){
    	cin>>u>>v;  --u;--v;
    	if(find(u)==find(v)){
    		cout<<"cycle detected"<<"\n";
    	}
    	merge(u , v);
    	arr[u].pb(v) ; arr[v].pb(u);
    }
    */
    int a,b;cin>>a>>b;
    cout<<((a|b) - (a&b))<<"\n";
    
}