using System;

using System.Collections.Generic;

using System.Globalization;

​

namespace NewCSharp

{

    class Program

    {

        static List<DateTime[]> result = new List<DateTime[]>();

        static int intervalsCount = 0;

        static void Main(string[] args)

        {

            string type;

            string[] dates;

​

            if (args.Length == 3)

            {

                type = args[0];

                dates = new string[2];

                dates[0] = args[1];

                dates[1] = args[2];

            }

            else

            {

                Console.Write("type: ");

                type = Console.ReadLine();

​

                Console.Write("startDate endDate: ");

                dates = Console.ReadLine().Split(" ");

            }

​

            if (dates.Length == 1)

            {

                throw new Exception("endDate is missing");

            }

​

            CultureInfo culture = new CultureInfo("ru-RU");

            DateTime startDate;

            DateTime endDate;

​

            if (!DateTime.TryParse(dates[0], culture, DateTimeStyles.None, out startDate))

            {

                throw new Exception("startDate is invalid");

            }

            if (!DateTime.TryParse(dates[1], culture, DateTimeStyles.None, out endDate))

            {

                throw new Exception("endDate is invalid");

            }

​

            if (startDate > endDate)

            {

                throw new Exception("startDate > endDate");

            }

​

            switch (type)

            {

                case "WEEK":

                    IntervalByWeeks(startDate, endDate);

                    break;

                case "MONTH":

                    IntervalByMonths(startDate, endDate);

                    break;

                case "QUARTER":

                    IntervalByQuarters(startDate, endDate);

                    break;

                case "YEAR":

                    IntervalByYears(startDate, endDate);

                    break;

                case "REVIEW":

                    IntervalByReviews(startDate, endDate);

                    break;

                default:

                    Console.WriteLine("unknown type");

                    break;

            }

​

            Console.WriteLine(intervalsCount);

            result.ForEach(Print);

​

            void Print(DateTime[] interval)

            {

                Console.WriteLine($"{interval[0].ToString("yyyy-MM-dd")} {interval[1].ToString("yyyy-MM-dd")}");

            }

        }

​

        static void IntervalByReviews(DateTime startDate, DateTime endDate)

        {

            for (DateTime i = startDate; i <= endDate;)

            {

                DateTime[] interval = new DateTime[2];

                interval[0] = i;

​

                if (i.Month >= 4 && i.Month <= 9)

                {

                    i = new DateTime(i.Year, 9, DateTime.DaysInMonth(i.Year, 9));

                }

                else

                {

                    i = new DateTime(i.Year + 1, 3, DateTime.DaysInMonth(i.Year + 1, 3));

                }

​

                interval[1] = i;

                if (i > endDate)

                {

                    interval[1] = endDate;

                }

​

                result.Add(interval);

                i = i.AddDays(1);

                intervalsCount++;

            }

        }

​

        static void IntervalByQuarters(DateTime startDate, DateTime endDate)

        {

            for (DateTime i = startDate; i <= endDate;)

            {

                DateTime[] interval = new DateTime[2];

                int monthsToAdd = 3 - (i.Month % 3);

                if (monthsToAdd == 3)

                {

                    monthsToAdd = 0;

                }

                interval[0] = i;

                i = i.AddMonths(monthsToAdd);

                i = new DateTime(i.Year, i.Month, DateTime.DaysInMonth(i.Year, i.Month));

                interval[1] = i;

                i = i.AddDays(1);

​

                result.Add(interval);

                intervalsCount++;

            }

        }

​

        static void IntervalByYears(DateTime startDate, DateTime endDate)

        {

            for (DateTime i = startDate; i <= endDate;)

            {

                DateTime[] interval = new DateTime[2];

​

                interval[0] = i;

                i = new DateTime(i.Year, 12, 31);

                if (i > endDate)

                {

                    interval[1] = endDate;

                }

                else

                {

                    interval[1] = i;

                }

​

                i = i.AddDays(1);

​

                result.Add(interval);

                intervalsCount++;

            }

        }

​

        static void IntervalByWeeks(DateTime startDate, DateTime endDate)

        {

            for (DateTime i = startDate; i <= endDate;)

            {

                DateTime[] interval = new DateTime[2];

​

                int weekDay = (int) i.DayOfWeek;

                if (weekDay == 0)

                {

                    weekDay = 7;

                }

                int daysToAdd = 7 - weekDay;

​

                interval[0] = i;

                interval[1] = i.AddDays(daysToAdd);

​

                if (interval[1] >= endDate)

                {

                    interval[1] = endDate;

                }

​

                result.Add(interval);

​

                i = interval[1].AddDays(1);

                intervalsCount++;

            }

        }

​

        static void IntervalByMonths(DateTime startDate, DateTime endDate)

        {

            for (DateTime i = startDate; i <= endDate; i = i.AddMonths(1))

            {   

                DateTime[] interval = new DateTime[2];

                if (i == startDate) 

                {

                    interval[0] = startDate;

                }

                else 

                {

                    interval[0] = new DateTime(i.Year, i.Month, 1);

                }

​

                if (i.Month == endDate.Month)

                {

                    interval[1] = endDate;

                }

                else

                {

                    interval[1] = new DateTime(i.Year, i.Month, DateTime.DaysInMonth(i.Year, i.Month));

                }

​

                result.Add(interval);

                intervalsCount++;

            }

        }

    }

}

​