using System;

public class Program

{

    public static void Main()

    {

        int valida = 420;

        int clave;

        do

        {

            Console.Write("Introduzca su clave numerica: ");

            clave = Convert.ToInt32(Console.ReadLine());

            if (clave != valida)

            Console.WriteLine("No valida!");

        }

        while (clave != valida);

        Console.WriteLine("Aceptada.");

    }

}