class IntSet11
{
// Destructive Set class, sets stored as unordered linked lists

 protected 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=ptr.next.next;
        }
 }

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

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

 protected static class Cell
 {
  int first;
  Cell next;

  Cell(int f,Cell n)
  {
   first=f;
   next=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+"}";
 }

}