import java.util.Set;
import java.util.HashSet;

class List {
    Node first;

    List () {
        this.first = null;
    }

    public void insert (Node n) {
        n.next = this.first;
        this.first = n;
    }

    public void print () {
        Node temp = new Node();
        temp.next = this.first;
        while (temp.next != null) {
            System.out.println(temp.next.str);
            temp = temp.next;
        }
    }

    public Node find (String s) {
        Node temp = new Node();
        temp.next = this.first;
        while (temp.next != null) {
            if (temp.next.str == s) return temp.next;
            temp = temp.next;
        }
        return null;
    }

    public void remove (String s) {
        Node temp = new Node();
        temp.next = this.first;
        Boolean run = true;
        while (temp.next != null && run) {
            if (temp.next.str == s) {
                temp.next = temp.next.next;
                run = false;
            }
            temp = temp.next;
        }
    }

    public void removeAll () {
        this.first = new Node ();
    }

    public void removeRepeats () {
        Node run = new Node();
        run.next = this.first;
        Set<String> repeats = new HashSet();
        while (run.next != null) {
            if (repeats.contains(run.next.str)) run.next = run.next.next;
            else {
                repeats.add(run.next.str);
                run = run.next;
            }
        }
    }

    public static List merge (List l1, List l2) {
        List merged = new List ();
        Node temp = l1.first;
        while (temp.next != null) {
            temp = temp.next;
        }
        temp.next = l2.first;
        merged.first = l1.first;
        return merged;
    }

    public static void main (String[] args) {
        /*
        List myList = new List ();
        myList.insert(new Node ("1"));
        myList.insert(new Node ("1"));
        myList.insert(new Node ("2"));
        myList.insert(new Node ("2"));
        myList.insert(new Node ("3"));
        myList.insert(new Node ("4"));
        myList.print();
        System.out.println(myList.find("2").str);
        myList.remove("3");
        myList.print();
        myList.removeRepeats();
        myList.print();
        myList.removeAll();
        myList.print(); */
        List l1 = new List ();
        List l2 = new List ();
        l1.insert(new Node ("1"));
        l1.insert(new Node ("2"));
        l1.insert(new Node ("3"));
        l2.insert(new Node ("4"));
        l2.insert(new Node ("5"));
        l2.insert(new Node ("6"));
        List l3 = List.merge(l1, l2);
        l3.print();
    }

}

class Node {
    String str;
    Node next;

    Node () {
        this.next = null;
    }

    Node (String s) {
        this.str = s;
        this.next = null;
    }
}