using System;

using System.Linq;

​

public class Program

{

    private static  Random r = new Random();

    private static string numbers = "0123456789";

    private static  string words = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

    public static void Main()

    {   

        var key = GetFirstSection() + "-" + GetSecondSection() + "-" + GetThirdSection();   

        Console.WriteLine(key.ToUpper());

    }

    private static  string GetFirstSection()

    {

        return GetRandomNumber() + GetRandomWord() + GetRandomNumber() + GetRandomWord();       

    }

    private static  string GetSecondSection()

    {

        var section = "";

        var character = GetRandomCharacter();

        var doubleCharacter = character + character;

        switch(r.Next(0, 3))

        {

            case 0 : 

            section = doubleCharacter + GetRandomCharacter() + GetRandomCharacter();

                break;

            case 1 : 

            section = GetRandomCharacter() + doubleCharacter + GetRandomCharacter();

                break;

            case 2 : 

            section = GetRandomCharacter() + GetRandomCharacter() + doubleCharacter;

                break;

        }

        return section;

    }

    private static  string GetRandomNumber() => numbers[r.Next(numbers.Length)].ToString();

    private static  string GetRandomWord() => words[r.Next(words.Length)].ToString();

    private static  string GetRandomCharacter()

    {

        if(r.Next(0, 2) > 0) 

        {

            return GetRandomNumber();

        }

        return GetRandomWord();

    }

    private static string GetThirdSection()

    {

        return GetRandomNumber() + GetRandomCharacter();

    }

}