class IntSet12
{
// Destructive Set class, sets stored as ordered linked lists

 private Cell list;

 public void delete(int n)
 {
  if(list!=null)
     if(list.first==n)
        list=list.next;
     else
        {
         Cell ptr;
         for(ptr=list; ptr.next!=null&&ptr.next.first<n; ptr=ptr.next) {}
         if(ptr.next!=null&&ptr.next.first==n)
            ptr.next=ptr.next.next;
        }
 }

 public void add(int n)
 {
  if(list==null)
     list = new Cell(n,null);
  else if(n<list.first)
     list = new Cell(n,list);
  else
     {
      Cell ptr;
      for(ptr=list; ptr.next!=null&&ptr.next.first<n; ptr=ptr.next) {}
      if(ptr.next==null||ptr.next.first>n)
         ptr.next = new Cell(n,ptr.next);
     }
 }

 public boolean member(int n)
 {
  Cell ptr;
  for(ptr=list; ptr!=null&&ptr.first<n; ptr=ptr.next) {}
  return (ptr!=null&&ptr.first==n);
 }

 public String toString()
 {
  String str="{";
  if(list!=null)
     {
      str+=list.first;
      for(Cell ptr=list.next; ptr!=null; ptr=ptr.next)
          str+=","+ptr.first;
     }
  return str+"}";
 }

 private static class Cell
 {
  int first;
  Cell next;
  
  Cell(int f,Cell n)
  {
   first=f;
   next=n;
  }
 }
}