using System;

public class Program

{

    public static void Main()

    {

        DateTime dt = DateTime.Now; 

        DayOfWeek startOfWeek = DayOfWeek.Monday;

        int diff = (7 + (dt.DayOfWeek - startOfWeek)) % 7;

        dt = dt.AddDays(-1 * diff).Date;

        Console.WriteLine(dt.ToString());

    }

}