Node Insert(Node head,int data) {
    return insertDS(head, data, head);
}
Node insertDS(Node head, int data, Node parent){
	if(head == null){
		head = new Node();
		head.data = data;
		if(parent != null) parent.next = head;
	}else
		insertDS(head.next, data, head);
	return head;
}