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

int a, b, c;

int main() {    
    cin >> a >> b >> c;

    if (a == b && b == c)
        cout << a << endl;
    else if (a == b)
        cout << c << endl;
    else if (b == c)
        cout << a << endl;
    else if (c == a)
        cout << b << endl;
    else
        cout << 6 - (a + b + c) << endl;
}