import java.util.NoSuchElementException;

public class OrderedList implements OrderedStructure {

    // Implementation of the doubly linked nodes (nested-class)

    private static class Node {

	private Comparable value;

	private Node previous;
	private Node next;

	private Node ( Comparable value, Node previous, Node next ) {
	    this.value = value;
	    this.previous = previous;
	    this.next = next;
	}
    }

    // Instance variables

    private Node head;
    private Node tail;

    // Representation of the empty list.

    public OrderedList() {
        head = null;
	tail = null;
    }

    // Calculates the size of the list

    public int size() {
	Node p = head;
	int count = 0;
	while ( p!=null ) {
	    p = p.next;
	    count++;
	}
	return count;
    }

    public Object get( int pos ) {
	throw new UnsupportedOperationException( "not implemented yet!" );
    }

    public boolean add( Comparable o ) {
	throw new UnsupportedOperationException( "not implemented yet!" );
    }

    public void remove( int pos ) {
	throw new UnsupportedOperationException( "not implemented yet!" );
    }
}