#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
using ll=long long;
using ld=long double;
ld pie=3.141592653589793;
ll mod=1000000007;
ld inf=10000999999999900;
int main(){
    ll a,b;
    cin >> a >> b;
    ll x=a|b;
    ll y=a&b;
    cout << x-y << endl;
}