class IntSet13
{
// Destructive Set class, sets stored as ordered trees

 private Cell tree;

 public void delete(int n)
 {
  Cell ptr=tree;
  if(tree.left==null&&tree.right==null)
     {
      if(tree.item==n)
         tree=null;
      return;
     }
  while(ptr!=null&&ptr.item!=n)
     if(n<ptr.item)
        {
         if(ptr.left!=null&&ptr.left.item==n&&
              ptr.left.left==null&&ptr.left.right==null)
            ptr.left=null;
         ptr=ptr.left;
        }
     else if(n>ptr.item)
        {
         if(ptr.right!=null&&ptr.right.item==n&&
              ptr.right.left==null&&ptr.right.right==null)
            ptr.right=null;
         ptr=ptr.right;
        }
  if(ptr!=null)
     if(ptr.left==null)
        {
         ptr.item=ptr.right.item;
         ptr.left=ptr.right.left;
         ptr.right=ptr.right.right;
        } 
     else if(ptr.right==null)
        {
         ptr.item=ptr.left.item;
         ptr.right=ptr.left.right;
         ptr.left=ptr.left.left;
        }
     else if(ptr.left.right==null)
        {
         ptr.item=ptr.left.item;
         ptr.left=ptr.left.left;
        }
     else
        {
         Cell ptr1=ptr.left;
         while(ptr1.right.right!=null)
            ptr1=ptr1.right;
         ptr.item=ptr1.right.item;
         ptr1.right=ptr1.right.left;
        }
 }

 public void add(int n)
 {
  if(tree==null)
     tree = new Cell(n,null,null);
  else
     {
      Cell ptr=tree;
      while(ptr.item!=n)
         if(n<ptr.item)
            {
             if(ptr.left==null)
                ptr.left = new Cell(n,null,null);
             ptr = ptr.left;
            }
         else if(n>ptr.item)
            {
             if(ptr.right==null)
                ptr.right = new Cell(n,null,null);
             ptr = ptr.right;
            }
     }
 }

 public boolean member(int n)
 {
  Cell ptr=tree;
  while(ptr!=null&&ptr.item!=n)
     if(n<ptr.item)
        ptr=ptr.left;
     else
        ptr=ptr.right;
  return ptr!=null;
 }

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

 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);
 }

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

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