#include "bits/stdc++.h"
#define rep(a,b) for(int a = 0;a < b;a++)
#define REP(i, x, n) for(int i = x; i < n; i++)
#define P(a) cout << a << endl
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
int dx[] = { 1, -1 , 0 , 0 };
int dy[] = { 0,  0,  1, -1 };
ll MOD = 1000000007;

void solve() {
    ll a, c;
    cin >> a >> c;
    a ^= c;
    P(a);
}

int main() {
    solve();
    return 0;
}