#include <iostream>
#include <iomanip>

class List;

class ListNode
{
   public:

      ListNode(const int &element, ListNode* nextPtr);
      friend class List;

   private:

      int num;
      ListNode* next;
};

class List
{
   public:

      List();

      void add(int myNum);
      void showList();
      void showListAddresses();

   private:

      ListNode* first;
};