public class Main {
    public static void printList(OListNode l) {
        for (; l!=null; l=l.next) {
            ((Obj)(l.val)).print();
            System.out.println();
        }
    }
    public static void printList(ListNode<Obj> l) {
        for (; l!=null; l=l.next) {
            l.val.print();
            System.out.println();
        }
    }
    public static void main(String [] args) {
        Person p1 = new Person(1234567890L,"Jane Doe");
        Person p2 = new Student(9876543210L,"John Smith", 1499999);
        Obj o3 = new Signed(7);
        OListNode l=null;
        //l=new OListNode(l,"acde");
        l=new OListNode(l,o3);
        l=new OListNode(l,p2);
        l=new OListNode(l,p1);
        printList(l);
        ListNode<Obj> k=null;
        k=new ListNode<Obj>(k,"acde");
        k=new ListNode<Obj>(k,o3);
        k=new ListNode<Obj>(k,p2);
        k=new ListNode<Obj>(k,p1);
        printList(k);
  }
}