public class Stack {
	
	private Node first ;
	
	private class Node
	{
		private Node next ;
		private int data ;
	}
	
	public boolean isEmpty()
	{
		return (first == null) ;
	}
	
	public void push(int newData)
	{
		Node oldfirst = first ;
		first = new Node() ;
		first.data = newData ;
		first.next = oldfirst ;
	}
	
	public int pop()
	{
		int returnVal = first.data ;
		first = first.next ;
		return returnVal ;
	}
	
	public static void main( String args[]) 
	{
		Stack s = new Stack() ;
		s.push(10) ;
		s.push(5) ;
		s.push(2) ;
		
		while (!s.isEmpty() ) 
		{
			System.out.println( s.pop() ) ;
		}
	}

}