uses graph, crt;
var d, m, x, y:integer;
begin
d:=detect; initgraph(d, m, '');
 x:=100;
 y:=100;

repeat
 repeat
     setcolor(white);
     circle(x, y, 20);
     delay(10);
     setcolor(black);
     circle(x, y, 20);
     x:=x+3;
     y:=y+3;
  until x>300;
 {    if x>300
then begin}
  repeat
     setcolor(white);
     circle(x, y, 20);
     delay(10);
     setcolor(black);
     circle(x, y, 20);
     x:=x+3;
     y:=y-3;
  until y<25;
  repeat
{then begin}
     setcolor(white);
     circle(x, y, 20);
     delay(10);
     setcolor(black);
     circle(x, y, 20);
     x:=x-3;
    { y:=y+3;}
 until x<15;
{end;
end;
end;}
until keypressed;
readln;
end.