// No.581 XOR
// https://yukicoder.me/problems/no/581
//

#include <iostream>
using namespace std;

int solve(int a, int c);


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

int solve(int a, int c) {
    int b = a ^ c;
    return b;
}