public static LinkedListNode addHelper(LinkedListNode a, LinkedListNode b, int increase) {
		if(a == null && b == null && increase == 0)
			return null;
			
		int sum = increase;
		if(a != null)
			sum += a.val;
		if(b != null)
			sum += b.val;
		
		LinkedListNode head = new LinkedListNode(sum%10);
		
		head.next = addHelper(a == null ? a : a.next ,b == null? b : b.next, increase/10);
		
		return head;
		
	}