class Node  {

  private Object  data;
  private Node  next;


  Node(Object  data)  {
    this(data, null);
  }

  Node(Object  data, Node  next)  {
    this.data = data;
    this.next = next;
  }

  Object  getData()  {
    return  data;
  }

  Node  getNext()  {
    return  next;
  }

  void  setData(Object  data)  {
    this.data = data;
  }

  void  setNext(Node  next)  {
    this.next = next;
  }
}

public class LinkedList  {

  private Node  head;

  public LinkedList()  {
    head = null;
  }

  private Node  getHead()  {
    return  head;
  }

   private void  setHead(Node  node)  {
    head = node;
  }

  public Object  getFirst() throws NullPointerException  {
    return  getHead().getData();
  }

  public boolean  isEmpty()  {
    return  getHead() == null;
  }

  public Object  get(int  index) throws NullPointerException  {
    Node  current = getHead();
    for (int  i = 0; i < index; ++i)  {
      current = current.getNext();
    }
    return  current.getData();
  }

  public boolean  add(Object  data)  {
    if (isEmpty())  {
      setHead(new  Node(data));
    }
    else  {
      Node  current = getHead();
      while (current.getNext() != null)  {
        current = current.getNext();
      }
      current.setNext(new  Node(data));
    }
    return  true;
  }

  public void  addFirst(Object  data)  {
    setHead(new  Node(data, getHead());
  }

  public Object  remove(int index) throws NullPointerException  {
    Object  temp;
    if (index == 0)  {
      temp = getHead().getData();
      setHead(getHead().getNext());
    }
    else  {
      Node  current = getHead();
      for (int  i = 0; i < index - 1; ++i)  {
        current = current.getNext();
      }
      temp = current.getNext().getData();
      current.setNext(current.getNext().getNext());
    }
    return  temp;
  }