using System;

public class Program

{

    public static void Main()

    {

        string color=Console.ReadLine();

        string green="green";

        switch (color)

        {

            case "green":

                Console.WriteLine("Go");

                break;

            case "yellow":

                Console.WriteLine("Slow Down");

                break;

            case "red":

                Console.WriteLine("Stop");

                break;

            default:

                Console.WriteLine("Inavlid Color");

                break;

        }

    }

}