// ordering
class color7 {
  private final String id;
  private final int ord;
  private color7 next;
  private color7 prev;

  private static int upperBound = 0;
  private static color7 first = null;
  private static color7 last = null;

  private color7(String mid) {
    id=mid;
    ord=upperBound++;
    if(first==null) first=this;
    if(last!=null) {
      this.prev=last;
      last.next=this;
    }
    last=this;
  }
  public String toString() {return id;}
  public int ord() {return ord;}
  public color7 next() {return next;}
  public color7 prev() {return prev;}

  public static int size() {return upperBound;}
  public static color7 first() {return first;}
  public static color7 last() {return last;}

  public static final color7 RED = new color7("red");
  public static final color7 GREEN = new color7("green");
  public static final color7 BLUE = new color7("blue");
}