(DEFUN PAINT(X1 Y1 X2 Y2 K)
  (SETQ A(LIST X1 Y1))
  (SETQ B(LIST X2 Y2))
  ;(COMMAND "ОТРЕЗОК"A B)
   (IF (= k 0)
    (PROGN
           (COMMAND "ОТРЕЗОК"A B)
    exit
   )
     ) 
  ; (DRAGON)
   
  (SETQ S1 (+ X1 X2))
   (SETQ S2 (- Y2 Y1))
   
   (SETQ S11 (/ S1 2))
   (SETQ S22 (/ S2 2))
   (SETQ TX (+ S11 S22))

  (SETQ Z1 (+ Y1 Y2))
  (SETQ Z2 (- X2 X1))
   
  (SETQ Z11 (/ Z1 2))
  (SETQ Z22 (/ Z2 2))
  (SETQ TY (- Z11 Z22))
  (SETQ KK(- K 1))
 

  (PAINT X2 Y2 TX TY KK)
  (PAINT X1 Y1 TX TY KK)
 
)
(DEFUN DRAGON()
 ;(setq X1 30 X2 30 Y1 30 Y2 300 K 0)
;(Paint X1 Y1 X2 Y2 K)
 (PAINT 100 150 500 150 8)
)

procedure Dragon(x1,y1,x2,y2,Depth:Longint;canv:TCanvas);
  procedure Paint(x1,y1,x2,y2,k:Longint);
  var tx,ty:Longint;
  begin
   if k=0 then
    begin
     canv.MoveTo(x1,y1);
     canv.LineTo(x2,y2);
     Exit;                      <===================== !!!
    end;
   tx:=(x1+x2) div 2+(y2-y1) div 2;
   ty:=(y1+y2) div 2-(x2-x1) div 2;
   Paint(x2,y2,tx,ty,k-1);
   Paint(x1,y1,tx,ty,k-1);
  end;
begin
 Paint(x1,y1,x2,y2,Depth);
end;