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

int main()
{
	int a, b, c;
	cin >> a >> b >> c;
	
	if(a == b && a == c) cout << a << endl;
	else if(a == b) cout << c << endl;
	else if(a == c) cout << b << endl;
	else if(b == c) cout << a << endl;
	else cout << 6 - a - b - c << endl;
	return 0;
}