Hi everybody, <br><br>We have found quite a simple decision in the page  <a href="http://ua.wikimedia.org/wiki/%D0%9E%D0%B1%D0%B3%D0%BE%D0%B2%D0%BE%D1%80%D0%B5%D0%BD%D0%BD%D1%8F:%D0%9A%D0%BE%D0%BD%D0%B2%D0%B5%D1%80%D1%82%D0%B0%D1%86%D1%96%D1%8F_%D1%81%D0%BF%D0%B8%D1%81%D0%BA%D1%96%D0%B2">http://ua.wikimedia.org/wiki/%D0%9E%D0%B1%D0%B3%D0%BE%D0%B2%D0%BE%D1%80%D0%B5%D0%BD%D0%BD%D1%8F:%D0%9A%D0%BE%D0%BD%D0%B2%D0%B5%D1%80%D1%82%D0%B0%D1%86%D1%96%D1%8F_%D1%81%D0%BF%D0%B8%D1%81%D0%BA%D1%96%D0%B2</a><br>
<br>Thanks everybody for your replies, especially interesting was Maarten&#39;s idea (though it does not work, but I believe must).<br><br>--<br>Andrij<br>