import java.util.*;
import java.util.zip.*;
import java.util.List;
import java.util.regex.*;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
import java.util.concurrent.locks.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
import javax.swing.table.*;
import java.io.*;
import java.net.*;
import java.lang.reflect.*;
import java.lang.ref.*;
import java.lang.management.*;
import java.security.*;
import java.security.spec.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.imageio.*;
import java.math.*;
class main {

static class LinkedTreeSet<A> extends AbstractSet<A> {
  Set<A> set;
  LinkedList<A> list = new LinkedList();
  
  LinkedTreeSet() { set = new TreeSet(); }
  LinkedTreeSet(Set<A> set) {
  this.set = set;}

  public int size() { return list.size(); }
  public Iterator<A> iterator() { return list.iterator(); }
  public boolean contains(Object o) { return set.contains(o); }
  
  public boolean add(A a) {
    if (!set.add(a)) return false;
    { list.add(a); return true; }
  }
  
  // TODO: optimize
  public boolean remove(Object o) {
    if (!set.remove(o)) return false;
    { list.remove(o); return true; }
  }
}
static <A> Iterator<A> iterator(Iterable<A> c) {
  return c == null ? emptyIterator() : c.iterator();
}


static Iterator emptyIterator() {
  return Collections.emptyIterator();
}

}