House Party

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class _03_HouseParty {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int n = Integer.parseInt(scanner.nextLine());

        List<String> listParty = new ArrayList<>();

        for (int i = 0; i < n; i++) {
            String input = scanner.nextLine();
            String[] data = input.split("\\s+");
            String name = data[0];
            String goingOrNot = data[2];

            if (data.length == 4){

                if (listParty.contains(name)){
                    listParty.remove(name);
                } else {
                    System.out.println(data[0] + " is not in the list!");
                }

            } else {
                if (!listParty.contains(name)){
                    listParty.add(name);
                } else {
                    System.out.println(data[0] + " is already in the list!");
                }
            }

        for (String name : listParty) {
            System.out.println(name);
        }
    }
}