/**
 * A node in a doubly-linked list.
 *
 * You must not modify this class.
 */

public class ListNode {

    // References to the next and previous nodes in the list, or null if
    // there isn't one.
    public ListNode next, previous;
    
    // Contents of the node.
    public Object contents;
    
    /**
     * Constructs a list node.
     * 
     * @param Object o object stored in the list node.
     *
     */
     
    public ListNode(Object o) {
    
        contents = o;
        
    }
}