#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
#include<iomanip>
using namespace std;

int main(){
    long long a, b, c;
    cin >> a >> c;
    b = a^c;
    cout << b << endl;
}