#include <algorithm>
#include <array>
#include <iostream>
#include <map>
#include <utility>
#include <vector>
#include <iomanip>
#include <sstream>
#include <climits>
#include <queue>
#include <list>

using namespace std;

int main()
{
    unsigned int a, b;

    while(cin >> a >> b)
    {
        cout << (a^b) << endl;
    }

    return 0;
}