#include <iostream>
#include <assert.h>

class stack_of_ints
{ protected:

    struct entry
    { int value;
      entry * next;
      entry(int, entry *); };

    entry * end;

  public:

    stack_of_ints();
    bool empty();
    void add(int);
    int take(); };

stack_of_ints :: entry :: entry(int v, entry * prev)
{ value = v;
  next = prev; }

stack_of_ints :: stack_of_ints()
{ end = NULL; }

bool stack_of_ints :: empty()
{ return end == NULL; }

void stack_of_ints :: add(int v)
{ end = new entry(v, end); }

int stack_of_ints :: take()
{ assert(end != NULL);
  int v = end->value;
  entry * old_end = end;
  end = end->next;
  delete old_end;
  return v; }

void main()
{ stack_of_ints s;
  s.add(1);
  s.add(3);
  s.add(5);
  s.add(7);
  s.add(9);
  s.add(11);
  s.add(13);
  while (! s.empty())
    cout << s.take() << "\n"; }