#include<iostream>
using namespace std;

int main() {
	int a, b, c;
	cin >> a >> b >> c;
	if (a == b and a == c) cout << a << endl;
	else if (a==b) cout << c << endl;
	else if (a == c) cout << b << endl;
	else if (c == b)cout << a << endl;
	else if(a+b+c==6) cout << 0 << endl;
	else if (a + b + c == 5) cout << 1 << endl;
	else if (a + b + c == 4) cout << 2 << endl;
	else if (a + b + c == 3) cout << 3 << endl;
	return 0;
}