using System;

public class Program

{

    public static void Main()

    {

        var s = RandomDigits(5);

        Console.WriteLine(s);

    }

    public static string RandomDigits(int length)

    {

        char[] alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();

        var random = new Random();

        string s = string.Empty;

​

        for (int i = 0; i < length; i++)

            s = String.Concat(s, alphabet[random.Next(0,26)] +" ");

​

        return s;

    }

}