with Ada.Text_IO, Ada.Integer_Text_IO;
use Ada.Text_IO, Ada.Integer_Text_IO;

procedure Lab4Tree is

  type Node is
    record
      Data : Integer := 0;
      Left : access Node := Null;
      Right : access Node := Null;
    end record;

  type Node_Ptr is access all Node;

  procedure PrintNode(Tree : access Node_Ptr; Indent : String) is
  begin
    Put(Indent);
    Put(Tree.Data, 4);
    New_Line;
    if Tree.Left /= Null then
      PrintNode(Tree.Left, Indent & " ");
    end if;
    if Tree.Right /= Null then
      PrintNode(Tree.Right, Indent & " ");
    end if;
  end PrintNode;

  procedure Print(Tree : access Node_Ptr) is
    Tmp : access Node_Ptr := Tree;
  begin
    if Tree = Null then
      Put_Line("Empty tree");
    else
      PrintNode(Tmp, "");
    end if;
  end Print;

  TreeInstance : Node_Ptr := Null;

begin
  Print(TreeInstance);
end Lab4Tree;