private static int addHelper( LinkedListNode l1, LinkedListNode l2, Stack<Integer> head ) {
		if ( l1.next == null && l2.next == null ) {
			int  sum  =  l1.data + l2.data ;
			head.push( sum % 10 );
			return   sum / 10;
		}
		int   carry = addHelper( l1.next, l2.next, head );
		int		sum = l1.data + l2.data + carry;
				
		head.push( sum % 10 );
		return  sum / 10;
	}