// AddDouble.java

class DoubleList<Type> {
    // a Node of the list
    private class Node {
        public Type data;
        public Node next;
        public Node prev;
    }

    // we store the head and tail
    private Node head;
    private Node tail;

    // the list starts empty
    public DoubleList() {
        head = null;
        tail = null;
    }

    // add a new value to the end
    public void append(Type value) {
        Node newNode = new Node();
        newNode.data = value;
        newNode.prev = tail;
        newNode.next = null;

        // set node before to point to new node, or head
        if (tail != null) {
            tail.next = newNode;
        } else {
            head = newNode;
        }

        tail = newNode;
    }
}

public class AddDouble {
    public static void main(String args[]) {
        // make the list
        DoubleList<Integer> list = new DoubleList<Integer>();

        // add some nodes at the end
        for (int i = 1;  i <= Integer.parseInt(args[0]); i++) {
            list.append(i * 10);
        }
    }
}