class Node
{
  int value;
  Node next;

  fn append(int val) Node
  {
    if (this.next == null)
    {
      Node tail = new Node;
      tail.value = val;
      tail.next = null;
      this.next = tail;
      return this;
    }

    this.next = this.next.append(val);
    return this;
  }

  fn sum() int
  {
    if (this.next == null)
      return this.value;

    return this.value + this.next.sum();
  }

  fn printList()
  {
    printline(this.value);
    if (this.next != null)
      this.next.printList();
  }
}

fn createList(int count) Node
{
  if (count <= 0)
    return null;

  Node head = new Node;
  head.value = count;
  head.next = createList(count - 1);
  return head;
}

printline("===== Test 1: factory & recursive escaping =====");
Node list = createList(3);
printline("Elements:");
list.printList();

printline("===== Test 2: mutation & methods =====");
list = list.append(10);
int total = list.sum();
printline("Sum of elements:");
printline(total);

if (total == 16)
  printline("Tests passed!");
else
{
  printline("Tests failed");
  exit(1);
}