#include <iostream>
#include <stdexcept>
 
template <typename T, int N>
class stack_type {
  T _base[N];
  int _front;
  int _back;
  int _size;
public:
  stack_type()
    : _front ( 0 ), _back ( 0 ), _size ( 0 )
  {}
 
  bool empty() const { return _size == 0; }
  bool full() const { return _size == N; }
 
  void push ( T data )
  {
    if ( full() )
      throw std::runtime_error ( "Stack is full" );
 
    _base[_back] = data;
 
    if ( ++_back == N )
      _back = 0;
 
    ++_size;
  }
 
  T pop()
  {
    if ( empty() )
      throw std::runtime_error ( "Stack is empty" );
 
    if ( --_back < 0 )
      _back = N - 1;
 
    --_size;
 
    return _base[_back];
  }
};
 
int main()
{
  stack_type<int, 3> stack;
 
  for ( int i = 5; !stack.full(); i-- )
    stack.push ( i );
 
  std::cout<< stack.pop() <<'\n';
  std::cout<< stack.pop() <<'\n';
 
  stack.push ( 2 );
  stack.push ( 1 );
 
  while ( !stack.empty() )
    std::cout<< stack.pop() <<'\n';
}