#include <bits/stdc++.h>
using namespace std;
int main(){
  int a, b, c;
  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;
  }
}