// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
int main() {
    // Input
    int a, b, c;
    cin >> a >> b >> c;

    // Ouptut
    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;
}