import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;

public class Football {

    private HashMap<String, ArrayList<String>> D;

    public Football() {
        D = new HashMap<>();
    }

    public void addClub(String club) {
        ArrayList<String> myArray = new ArrayList<>();
        D.put(club, myArray);
    }

    public void addFootballPlayer(String club, String player) {
        if (!D.containsKey(club)) {
            return;
        }
        D.get(club).add(player);

    }

    public Iterator<String> getClubs(String player) {
        ArrayList<String> myarray = new ArrayList<>();

        for (String club : D.keySet()) {
            if (D.get(club).contains(player)) {
                myarray.add(club);
            }
        }

        if (myarray.size() == 0) {
            return null;
        }
        return myarray.iterator();
    }

    public int getClubCount(String player) {
        ArrayList<String> myarray = new ArrayList<>();

        for (String club : D.keySet()) {
            if (D.get(club).contains(player)) {
                myarray.add(club);
            }
        }

        return myarray.size();
    }

    public Iterator<String> getCommonClubs(String player1, String player2) {
        if (getClubCount(player1) == 0 || getClubCount(player2) == 0) {
            return null;
        }

        ArrayList<String> myarray = new ArrayList<>();

        for (String club : D.keySet()) {
            if (D.get(club).contains(player1) && D.get(club).contains(player2)) {
                myarray.add(club);
            }
        }

        if (myarray.size() == 0) {
            return null;
        }
        return myarray.iterator();

    }

    public Iterator<String> getPlayers(String club, int n) {
        if (!D.containsKey(club)) {
            return null;
        }
        ArrayList<String> result = new ArrayList<>();
        ArrayList<String> myarray = new ArrayList<>();
        for (String player : D.get(club)) {
            myarray.add(player);
        }

        for (int t = 0; t < n; t++) {
            if (myarray.size()>0) {
                int anscount = 0;
                String ansname = "";
                for (String player : myarray) {
                    int k = getClubCount(player);
                    if (k > anscount) {
                        anscount = k;
                        ansname = player;
                    }
                }

                myarray.remove(ansname);
                result.add(ansname);
            }
        }
        return result.iterator();
    }
}