template <class Item>
class Stack
{
	struct Element
	{
		double inf;
		Element *next;
		Element(double x, Element *p) : inf(x), next(p)
		{
		}
	};
	Element *head;
public:
	Stack() :head(0)
	{
	}
	bool Empty()
	{
		return head == 0;
	}
	double Pop()
	{
		if (Empty())
		{
			return 0;
		}
		Element *r = head;
		double i = r->inf;
		head = r->next;
		delete r;
		return i;
	}
	void Push(double data)
	{
		head = new Element(data, head);
	}
	double Top()
	{
		if (Empty())
		{
			return 0;
		}
		else
		{
			return head->inf;
		}
	}
};