using System;

namespace calendar
{
    class Program
    {
        static int day_1;
        static int month_1;
        static int year_1;
        static int day_2;
        static int month_2;
        static int year_2;
        static int increase_amount;

        static int TakeMonthName(string month)
        {
            switch (month.ToLower())
            {
                case "january":
                    return 1;
                case "february":
                    return 2;
                case "march":
                    return 3;
                case "april":
                    return 4;
                case "may":
                    return 5;
                case "june":
                    return 6;
                case "july":
                    return 7;
                case "august":
                    return 8;
                case "september":
                    return 9;
                case "october":
                    return 10;
                case "november":
                    return 11;
                case "december":
                    return 12;
                default:
                    return 0;
            }
        }
        static string TakeMonthInt(int month)
        {
            //for translating month name to integer
            switch (month)
            {
                case 1:
                    return "january";
                case 2:
                    return "february";
                case 3:
                    return "march";
                case 4:
                    return "april";
                case 5:
                    return "may";
                case 6:
                    return "june";
                case 7:
                    return "july";
                case 8:
                    return "august";
                case 9:
                    return "september";
                case 10:
                    return "october";
                case 11:
                    return "november";
                case 12:
                    return "december";
                default:
                    return "undefined";
            }

        }
        static string GetMonthsSeasons(int month)
        {
            switch (month)
            {
                case 12:
                case 1:
                case 2:
                    return "winter";
                case 3:
                case 4:
                case 5:
                    return "spring";
                case 6:
                case 7:
                case 8:
                    return "summer";
                case 9:
                case 10:
                case 11:
                    return "autumn";
                default:
                    return "undefined";
            }

        }  
        static int GetNullDay(int month)
        {
            switch (month)
            {
                case 1:
                    return 1;
                case 2:
                    return 12;
                case 3:
                    return 5;
                case 4:
                    return 2;
                case 5:
                    return 7;
                case 6:
                    return 4;
                case 7:
                    return 9;
                case 8:
                    return 6;
                case 9:
                    return 3;
                case 10:
                    return 8;
                case 11:
                    return 12;
                case 12:
                    return 10;
                default:
                    return 1200;


            }
        }
        static string GetDayNames(int day, int month, int year)
        {
            int NullDay = GetNullDay(month);
            string yearString = Convert.ToString(year);

            // this is for the numbers of formula   
            string centuryS = yearString.Substring(0, 2);
            int century = Convert.ToInt32(centuryS);

            int yearC_control = year - century * 100;
            int yearC_4 = yearC_control % 10;
            int yearC_3 = (yearC_control - yearC_4) / 10;
            
            double W_0 = (yearC_4 / 4) - (yearC_3 / 2);
            double W_1 = Math.Round(W_0);
            if (W_0 < W_1)
            {
                W_1 += W_1 - 1;
                W_1--;
            }

            double WoDN_1 = day - NullDay + yearC_4 - yearC_3 + W_1 - (2 * (century % 4));
            double weekofday_number;
            while (WoDN_1 < 0) 
            {
                WoDN_1 += WoDN_1 + WoDN_1;
                WoDN_1++;
            }

            weekofday_number = WoDN_1 % 7;

            switch (weekofday_number)
            {
                case 1:
                    return "monday";
                case 2:
                    return "tuesday";
                case 3:
                    return "wednesday";
                case 4:
                    return "thursday";
                case 5:
                    return "friday";
                case 6:
                    return "saturday";
                case 0:
                    return "sunday";
                default:
                    return "undefined";
            }
        }
        static bool isLeapYear(int year)
        {
            if (year % 4 == 0 && year % 100 != 0) return true;
            else if (year % 400 == 0 && year % 4000 != 0) return true;
            else return false;
        }
        static int exceptDayLength(int month, int year)
        {
            if (month == 2) return isLeapYear(year) ? 29 : 28;
            int monthd = month % 2;
            if (month <= 7) return monthd == 1 ? 31 : 30;
            return monthd == 1 ? 30 : 31;
        }
        static void getDate1()
        {
            int day = 0;
            string month = "month";
            int year = 0;
            bool isValid = false;
            Console.WriteLine("Getting date 1");
            while (!isValid)
            {
                try
                {
                    Console.WriteLine("Please enter the day as a number.");
                    day = Convert.ToInt32(Console.ReadLine());
                    Console.WriteLine("Please enter the month as string. ");
                    month = Console.ReadLine();
                    Console.WriteLine("Please enter the year.");
                    year = Convert.ToInt32(Console.ReadLine());
                    isValid = validate(day, month, year);
                }
                catch
                {
                    isValid = false;
                }
                if (!isValid)
                {
                    Console.WriteLine("please enter a valid date");
                    Console.WriteLine("Getting date 1");
                }
            }
            day_1 = day;
            month_1 = TakeMonthName(month);
            year_1 = year;
        }
        static void getDate2()
        {
            int day = 0;
            string month = "month";
            int year = 0;
            bool isValid = false;
            Console.WriteLine("Getting date 2");
            while (!isValid)
            {
                try
                {
                    Console.WriteLine("Please enter the day as a number.");
                    day = Convert.ToInt32(Console.ReadLine());
                    Console.WriteLine("Please enter the month as string. ");
                    month = Console.ReadLine();
                    Console.WriteLine("Please enter the year.");
                    year = Convert.ToInt32(Console.ReadLine());
                    isValid = validate(day, month, year);
                }
                catch
                {
                    isValid = false;
                }
                if (!isValid)
                {
                    Console.WriteLine("please enter a valid date");
                    Console.WriteLine("Getting date 2");
                }
            }
            day_2 = day;
            month_2 = TakeMonthName(month);
            year_2 = year;
        }
        static bool validate(int day, string month, int year)
        {
            int monthIndex = TakeMonthName(month);
            if (year > 10000 || year < 2015) return false;
            if (monthIndex == 0) return false;
            if (day > exceptDayLength(monthIndex, year)) return false;
            if (day <= 0) return false;
            return true;
        }
        static void checkDates()
        {
            static bool valid()
            {
                if (year_2 < year_1) return false;
                if (month_2 < month_1 && year_2 == year_1) return false;
                if (day_2 < day_1 && month_1 == month_2 && year_1 == year_2) return false;
                return true;
            }
            bool isValid = valid();

            if (!isValid)
            {
                Console.WriteLine("the second date mus be later than first date");
                getDate2();
                checkDates();
            }
        }
        static void printCalendar()
        {
            int extraDay = 0;
            string currentSeason = "";
            for (int year = year_1; year <= year_2; year++)
            {
                int exceptMonth = year == year_2 ? month_2 : 12;
                int startMonth = year == year_1 ? month_1 : 1;

                for (int month = startMonth; month <= exceptMonth; month++)
                {
                    if (currentSeason != GetMonthsSeasons(month))
                    {
                        currentSeason = GetMonthsSeasons(month);
                        Console.WriteLine(currentSeason);
                    }

                    int exceptDay = year == year_2 && month == month_2 ? day_2 : exceptDayLength(month, year);
                    int startDay = year == year_1 && month == month_1 ? day_1 : 1;
                    startDay += extraDay;
                    for (int day = startDay; day <= exceptDay;)
                    {
                        Console.WriteLine(day + " " + TakeMonthInt(month) + " " + year + " " + GetDayNames(day, month, year));
                        day += increase_amount;
                        if (day > exceptDay)
                        {
                            extraDay = day - exceptDay - 1;
                        }
                        if (day == exceptDay)
                        {
                            extraDay = 0;
                        }
                    }
                }
            }
        }
        static void Main(string[] args)
        {
            getDate1();
            getDate2();
            checkDates();
            Console.WriteLine("Please enter the increase amount of the days.");
            increase_amount = Convert.ToInt32(Console.ReadLine());
            printCalendar();
            //for null days

        }
    }
}