static SinglyLinkedListNode insertNodeAtTail(SinglyLinkedListNode head, int data) {
        
        SinglyLinkedListNode curr = head;
        SinglyLinkedListNode n1 = new SinglyLinkedListNode(data);
        
        if(head == null)
        {
            head = n1;
            Console.WriteLine(head.data);
        }
        else
        {
            if(curr.next == null)
                head.next = n1;
            else
            {
                while(curr.next != null)
                    curr = curr.next;
                
                curr.next = n1;
            }
            Console.WriteLine(head.next.data);
        }
        
        return head;
    }