class Range implements Serializable {

    public static List<String> getDays(List<Range> ranges)
    {
        List<Range> normalizedRanges = normalize(ranges);
        Set<String> daysSet = new HashSet<>();
        for (Range range : normalizedRanges)
        {
            daysSet.add(range.st);
        }
        List<String> result = new ArrayList<>(daysSet);
        Collections.sort(result);
        return result;
    }

    public  Range();
    public  Range(String st, String ed, String sh, String eh);

}