Uses Graph;
var
  g,s,i : integer;
Begin
  InitGraph(g,s,'');
  SetWriteMode(XORput);
  for i := 0 to 80 do
   begin
     SetColor(1);
     Line(150,400,150+I*2,80);
     SetColor(2);
     Line(150,80,470,80+I*2);
     SetColor(4);
     Line(470,80,470-I*2,400);
     SetColor(8);
     Line(470,400,150,400-I*2);
   end;
  for i := 0 to 80 do
   begin
     SetColor(1);
     Line(150,400,470,80+I*2);
     SetColor(2);
     Line(150,80,470-I*2,400);
     SetColor(4);
     Line(470,80,150,400-i*2);
     SetColor(8);
     Line(470,400,150+i*2,80);
   end;
  ReadLn;
  CloseGraph;
end.