using System;

using System.Globalization;

using System.Security.Cryptography;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Pad(1));

    }

    private const string Letters = "BCDGHJKLMNPQRSTV"; // 16 characters

    private const int ApiIdLength = 33; // one more than a GUID

    private static string Pad(int databaseId)

    {

        var apiId = databaseId.ToString(CultureInfo.InvariantCulture) + @"A";

        var md5 = MD5.Create();

        var hash = md5.ComputeHash(BitConverter.GetBytes(databaseId));

        var i = 0;

​

        while (apiId.Length < ApiIdLength)

        {

            var bits = hash[i/2];

            if (i % 2  == 0)

            {

                bits = (byte) (bits >> 4);

            }

            else

            {

                bits = (byte) (bits & 0x0F);

            }

            apiId += Letters[bits];

            i++;

            if (i/2 > hash.Length)

            {

                i = 0;

            }

        }

        return apiId;

    }

}