program kruznica;
uses crt,graph;
var drajver,rezim,pom:integer;
    x,y,r1,r:integer;
begin
  ClrScr;
  write(' Program crta kruznicu u centru ekrana');
  writeln;
  write(' Unesi poluprecnik u intervalu [0,29]: ');
  readln(r1);
  r:=r1*10;
  drajver:=detect;
  initgraph(drajver,rezim,'');
  if (r1>0) and (r1<29)
    then
    begin
      x:=(getmaxX+1) div 2;
      y:=(getmaxY+1) div 2;
      circle(x,y,r);
      readln;
      closegraph;
    end
    else
    begin
      write(' Krug se za dati poluprecnik ne vidi na ekranu!');
      readln
    end
end.