public static function getPagesCount($linesNumber, $divider) {
        if ($linesNumber < 0 || $divider < 0) {
            return -1;
        }
        $pagesCount = intval($linesNumber / $divider);
        if (0 < ($linesNumber % $divider)) {
            ++$pagesCount;
        }
        return $pagesCount;
    }