using System;

public class Program

{

    public static void Main()

    {

        int year = 2023;

        int month = 5;

​

        DateTime firstDayOfMonth = new DateTime(year, month, 1);

        int daysInMonth = DateTime.DaysInMonth(year, month);

​

        DayOfWeek firstDayOfWeek = firstDayOfMonth.DayOfWeek;

        int offset = (int)DayOfWeek.Saturday - (int)firstDayOfWeek;

​

        if (offset < 0) offset += 7;

​

        Console.WriteLine(firstDayOfMonth.ToString("MMMM yyyy"));

        Console.WriteLine();

        Console.WriteLine(" Sa Su Mo Tu We Th Fr");

​

        for (int i = 0; i < offset; i++) {

            Console.Write("   ");

        }

​

        for (int day = 1; day <= daysInMonth; day++) {

            Console.Write($"{day,3}");

            if ((offset + day) % 7 == 0) {

                Console.WriteLine();

            }

        }

​

        if ((offset + daysInMonth) % 7 != 0) {

            Console.WriteLine();

        }

    }

}