ABC_203_A.cpp

#include <iostream>
#include <algorithm>
using namespace std;

int main() {
	int a[3];
	cin >> a[0] >> a[1] >> a[2];
	sort(a, a + 3);

	if (a[0] == a[1])
	{
		cout << a[2] << endl;
	}
	else if(a[1] == a[2])
	{
		cout << a[0] << endl;
	}
	else
	{
		cout << 0 << endl;
	}
}