class List {
private:

  class Node {
  public:
    int data;
    Node * next;
    Node (int data, Node *next) {
      Node::data = data; Node::next = next;
    }
  };

  Node *head;

public:

  List () { head = NULL; };

  ~List ();

  // outputs list contents to cout
  void outputList () const;

  // adds a value to the list
  void insert (int value);

};