public class stackofints<Item>
{
    private static node topofstack=null;

    private static class node{
        Item item;
        node next;
    }

    public static void push(Item item){
        node oldtopofstack=topofstack;
        topofstack=new node();
        topofstack.item=item;
        topofstack.next=oldtopofstack;
    }
    public static int pop(){
        Item item=topofstack.item;
        topofstack=topofstack.next;
        return item;
    }
    public boolean isEmpty(){return topofstack==null;}
    public static Item size(){
        Item i=0;
        node iterate=topofstack;
        while(iterate!=null)
        {
            iterate=iterate.next;
            i++;
        }
        return i;
    }

    public static void main(String[] args)
    {
        push(1);
        push(2);
        push(3);
        System.out.println(size());

    }

}