procedure TMainForm.btnBTreeClick(Sender: TObject);
var
   I, Len: Integer;
begin
   Randomize;
   Len := StrToInt(edtA.Text);
   SetLength(Arr, Len);
   for I := 0 to Len - 1 do
   begin
      Arr[I] := 1 + Random(Len);
      if Tree = nil then
         Tree := TBTree.Create(Arr[I])
      else
         Tree.Add(Arr[I]);
   end;
   fCanvas := TCanvasForm.Create(Self);
   fCanvas.Show;
   DrawTree(MAX_WIDTH div 2, MAX_HEIGHT div Tree.Depth div 2,
     MAX_CANVAS_WIDTH div 2, MAX_HEIGHT div Tree.Depth, RADIUS, Tree,
     fCanvas.Canvas);
   Tree.Destroy;
   Tree := nil;
end;