using System;

public class Program

{

    public static void Main(string[] args)

    {

        Movie avengers = new Movie ("The Avengers", "Joss Whedon", "PG-13");

        Movie shrek = new Movie ("Shrek", "Adam Adamson", "PG");

        shrek.Rating = "dog";

        Console.WriteLine(shrek.Rating);

        Console.ReadLine();

    }

    class Movie 

    {

        public string title;

        public string director;

        private string rating;

        public Movie(string aTitle, string aDirector, string aRating)

        {

           title = aTitle;

           director = aDirector;

           Rating = aRating;

        }

        public string Rating

        {

            get{return rating;}

            set{

                if(value == "G" || value == "PG" || value == "PG-13"|| value ==  "R"|| value == "NR")

                {

                    rating = value;

                }

                else

                {

                    rating = "NR";

                }

            }

        }

    }

}