import java.util.*;

class Node {
    int data;
    Node next;
    Node prev;

    Node(int data) {
        this.data = data;
        this.next = null;
        this.prev = null;
    }
}

class LinkedList {
    Node head, tail,safe;

    public void insert(int data) {
        Node newNode = new Node(data);

        if (head == null) {
            head = newNode;
            tail = newNode;
        } else {
            tail.next = newNode;
            safe = tail;
            tail = newNode;
            tail.prev = safe;

        }
    }

    public void display() {
        Node temp = head;
        while (temp != null) {
            System.out.println(temp.prev+" "+temp.data + " "+temp.next);
            temp = temp.next;
        }
        System.out.println();
    }
}

public class Test {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        LinkedList list = new LinkedList();
        // list.insert(10);
        // list.insert(20);
        // list.insert(30);
        // list.insert(40);
        // list.insert(50);
        // list.insert(60);
        int data;
        while(true)
        {
            data = sc.nextInt();
            if(data == -1){
                break;
            }
            list.insert(data);
        }
         list.display();
    }
}