#include "bits/stdc++.h"

using namespace std;
using ll = long long;
using IP = pair<int, int>;

const ll INF = 1LL << 62;
#define atcoder(int)1e9+7
#define Endl endl
#define mp make_pair
#define all(v) v.begin(),v.end()
#define pb push_back

ll gcd(ll a, ll b) {//最大公約数
	if (a%b == 0)return b;
	else gcd(b, a%b);
}

ll lcm(ll a, ll b) {//最小公倍数
	return (a / gcd(a, b))*b;
}

int main() {

	ll a, c;

	cin >> a >> c;

	ll b = a^c;

	cout << b << endl;

	return 0;
}