private boolean isValidWorkHour(String shouldWork) {
        return (shouldWork.equalsIgnoreCase("z")
                || shouldWork.equalsIgnoreCase("v")
                || shouldWork.equalsIgnoreCase("c")
                || shouldWork.equalsIgnoreCase("k")
                || shouldWork.equals("*")
                || shouldWork.matches("[0-2]\\d{3}-[0-2]\\d{3}"));
    }