function workbook($n, $k, $arr) {
    $result = array_fill(0, array_sum($arr), []);
    $pages = 0;
    $specials = 0;

    foreach ($arr as $numPages) {
        for ($problem = 1; $problem <= $numPages; $problem++) {
            if (count($result[$pages]) >= $k || $problem === 1) {
                $pages++;
            }
            $result[$pages][] = $problem;
        }
    }

    for ($i = 1; $i < count($result); $i++) {
        if (in_array($i, $result[$i])) {
            $specials++;
        }
    }

    return $result;
}