using System;

public class Program

{

    public static void Main()

    {  int hora;

        Console.WriteLine(" introduce la edad " );

        hora = int.Parse(Console.ReadLine());

if ( hora < 12 ) {

    Console.WriteLine(" BUENOS DIAS " );

} else { 

            if ( ( hora > 12 ) && ( hora < 18 ) )   

                Console.WriteLine(" BUENAS TARDES " );

        else {

            if ( hora > 18 ) 

                Console.WriteLine(" BUENAS NOCHES " );

    } } }}