class IntSet16
{
// Destructive Set class, sets stored as ordered trees
// Recursive methods used

 private Cell tree;

 public void delete(int n)
 {
  if(tree!=null)
     if(tree.left==null&&tree.right==null)
        {
         if(tree.item==n)
            tree=null;
        }
     else
        delete(n,tree);
 }

 private static void delete(int n,Cell t)
 {
  if(n<t.item)
    if(t.left.left==null&&t.left.right==null)
       {
        if(t.left.item==n)
           t.left=null; 
       }
    else
       delete(n,t.left);
  else if(n>t.item)
     if(t.right.left==null&&t.right.right==null)
        {
         if(t.right.item==n)
            t.right=null;
        }
     else
        delete(n,t.right);
  else if(t.left==null)
     {
      t.item=t.right.item;
      t.right=t.right.right;
     }
  else if(t.left.right==null)
     {
      t.item=t.left.item;
      t.left=t.left.left;
     }
  else
      t.item = removeRightmost(t.left);
 }

 private static int removeRightmost(Cell t)
 {
  if(t.right.right==null)
     {
      int rightmost = t.right.item;
      t.right = t.right.left;
      return rightmost;
     }
  else
     return removeRightmost(t.right);
 }

 public void add(int n)
 {
  if(tree==null)
     tree = new Cell(n,null,null);
  else
     add(n,tree);
 }

 private static void add(int n,Cell t)
 {
  if(n<t.item)
     if(t.left==null)
        t.left = new Cell(n,null,null);
     else
        add(n,t.left);
  else if(n>t.item)
     if(t.right==null)
        t.right = new Cell(n,null,null);
     else
        add(n,t.right);
 }

 public boolean member(int n)
 {
  return member(n,tree);
 }

 private static boolean member(int n,Cell t)
 {
  if(t==null)
     return false;
  else if(t.item==n)
     return true;
  else if(n<t.item)
     return member(n,t.left);
  else
     return member(n,t.right);
 }

 public String toString()
 {
  return "{"+toString(tree)+"}";
 }

 public String treeString()
 {
  return treeString("",tree);
 }

 private static String treeString(String indent,Cell tree)
 {
  if(tree==null)
     return "\n";
  else if(tree.left==null&&tree.right==null)
     return indent+tree.item+"\n";
  else
    return treeString(indent+"     ",tree.right)+
           indent+tree.item+"\n"+
           treeString(indent+"     ",tree.left);
 }

 private static String toString(Cell tree)
 {
  if(tree==null)
     return "";
  else if(tree.left==null&&tree.right==null)
     return ""+tree.item;
  else if(tree.left==null)
     return tree.item+","+toString(tree.right);
  else if(tree.right==null)
     return toString(tree.left)+","+tree.item;
  else
     return toString(tree.left)+","+tree.item+","+toString(tree.right);
 }

 private static class Cell
 {
  int item;
  Cell left,right;
  
  Cell(int n,Cell l,Cell r)
  {
   item=n;
   left=l;
   right=r;
  }
 }
}