using System;

public class Program

{

    public static void Main()

    {

        var startOfLastMonth = DateTime.Today

            .AddDays(-DateTime.Today.Day+1)

            .AddMonths(-1);

        Console.WriteLine(startOfLastMonth);

        startOfLastMonth = new DateTime(DateTime.Today.Year, DateTime.Today.Month, 1)

            .AddMonths(-1);

        Console.WriteLine(startOfLastMonth);

    }

}