using System;

public class Program

{

    public static void Main()

    {   

        var date0 = DateTime.Now.AddDays(6);

        var date1 = DateTime.Now;

        var date2 = DateTime.Now.AddDays(-1);

        var date3 = DateTime.Now.AddDays(-2);

        var date4 = DateTime.Now.AddDays(-3);

        var date5 = DateTime.Now.DayOfYear;

        var date6 = 6 - (12 + date5 - (int)date1.DayOfWeek) % 7;

        var date7 = 1 + (8 - date6) % 7;

        var date8 = DateTime.Now.DayOfWeek;

        var weekNumberTest0 = GetFinancialWeekNumber(date0);

        var weekNumberTest1 = GetFinancialWeekNumber(date1);

        var weekNumberTest2 = GetFinancialWeekNumber(date2);

        var weekNumberTest3 = GetFinancialWeekNumber(date3);

        var weekNumberTest4 = GetFinancialWeekNumber(date4);

        Console.WriteLine(weekNumberTest0 +" "+ date0); 

        Console.WriteLine(weekNumberTest1 +" "+ date1); 

        Console.WriteLine(weekNumberTest2 +" "+  date2);

        Console.WriteLine(weekNumberTest3 +" "+  date3);

        Console.WriteLine(weekNumberTest4 +" "+ date4);

        Console.WriteLine("Day of Year:" +" " + date5);

        Console.WriteLine("Jan1DayOfWeek:" +" "+ date6);

        Console.WriteLine("Start Of First Week:" +" "+ date7);

        Console.WriteLine("Day number of Today:" + " " + (int)date8);

    }

        public static int GetFinancialWeekNumber(DateTime today)

        {

            bool isLeapYear = DateTime.IsLeapYear(today.Year);

            int dayOfYear = today.DayOfYear; // Day of the year (1-365/366)

            DateTime jan1 = new DateTime(today.Year, 1, 1); // January 1st of the current year

            int jan1DayOfWeek = (int)jan1.DayOfWeek; // Day of the week for Jan 1 (0 = Sunday, 6 = Saturday)

​

            // Calculate the first Monday of the new year

            DateTime firstMondayOfNewYear = jan1.AddDays((8 - jan1DayOfWeek) % 7);

​

            // Special case: Return 52 if today is in the last week of the year, and the year is not ending on a Friday

            DateTime lastDayOfYear = new DateTime(today.Year, 12, 31); // December 31st

            int lastDayOfWeek = (int)lastDayOfYear.DayOfWeek; // Day of the week for December 31st

​

            // If the last day of the year is not a Friday, return 52 for all days until the first Monday of the new year

            if (today >= firstMondayOfNewYear || lastDayOfWeek != 5)

            {

                return 52;

            }

​

            // Calculate the first Monday of the year as the start of week 1

            DateTime startOfFirstWeek = jan1.AddDays((8 - jan1DayOfWeek) % 7); // First Monday of the year

​

            // If the current date is before the first Monday, return week 52

            if (today < firstMondayOfNewYear)

            {

                return 52;

            }

​

            // Calculate the ISO week number for other dates

            int startOfFirstWeekOffset = (8 - jan1DayOfWeek) % 7 + 1;  // Monday start

​

            if (dayOfYear >= startOfFirstWeekOffset)

            {

                int adjustment = startOfFirstWeekOffset - 1;

                return 1 + (dayOfYear - adjustment - 1) / 7;

            }

            else

            {

                return 1; // First week of the year

            }

        }

}