private static function _getMorphed($n, $f1, $f2, $f5) {
        $n  = abs($n) % 100;
        $n1 = $n % 10;
        if ($n > 10 && $n < 20) return $f5;
        if ($n1 > 1 && $n1 < 5) return $f2;
        if ($n1 == 1) return $f1;

        return $f5;
    }