using System;

public class Program

{

    public static void Main()

    {

        int time;

        time= Convert.ToInt16(Console.ReadLine());

        if (time <10)

        {

        Console.WriteLine("buenos dias");

        }

        else if (time <20)

        {

            Console.WriteLine("buenas tardes");

        }

        else

        {

            Console.WriteLine("buenas noches");

        }

    }

}