03. Periodic Table

package DPM;

import java.util.Scanner;
import java.util.TreeSet;

public class Main {
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        int num = scan.nextInt();
        TreeSet<String > elements = new TreeSet<>();
        for (int i = 0; i < num; i++) {
            String[] line = scan.nextLine().split(" ");
            for (int j = 0; j < line.length; j++) {
                elements.add(line[j]);

            }

        }
        for (String element : elements) {
            System.out.print(element+ " ");
        }
    }
}