#include <bits/stdc++.h>
using namespace std;

#define rep(i, n) for (int i = 0; i < (n); i++)
using ll = unsigned long long;
using Graph = vector<vector<int>>;

int main()
{
    int a, b;
    cin >> a >> b;
    string a_s = to_string(a), b_s = to_string(b);
    a = stoi(a_s, 0, 2);
    b = stoi(b_s, 0, 2);
    a = (a ^ b);
    cout << a << endl;
}