using System;

public class Program

{

    public static void Main()

    {

        string msg = "-1 hello world";

        string[] words = msg.Split(' ');

        int number;

        if (int.TryParse(words[0], out number)) {

            Console.WriteLine("Digit! " + words[0]);

        } else {

            Console.WriteLine("Not a Digit!");

        }

    }

}