program Loptica;
uses Graph,Crt;
var xl,xd:integer;
procedure Inicijalizacija;
     var  GraphDriver,GraphMode:integer;
     begin
       GraphDriver:=Detect;
       InitGraph(GraphDriver,GraphMode,'');
       if GraphResult<>grOk then
         begin
           writeln(' Greska...kraj programa');
           halt(1)
         end
     end;
procedure horizontkret(xl,xd:integer);
var dx,x,y,r:integer;
begin
  dx:=1; r:=10;
  x:=xl+round((xd-xl)/2);
  y:=round(GetMaxY/2);
  repeat
    if ((xl+r<x)and(x<xd-r))
      then
        begin
          SetColor(white);Circle(x,y,r);Delay(10);
          SetColor(black);Circle(x,y,r)
        end
      else dx:=-dx;
      x:=x+dx;
      until keypressed
      end;
      begin
        writeln(' Unesite levu i desnu granicu (0,GetMaxY)' );
        readln(xl,xd);
        Inicijalizacija;
        Line(xl,0,xl,GetMaxY);Line(xd,0,xd,GetMaxY);
        horizontkret(xl,xd);
        CloseGraph
end.