using System;

using System.Text;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Console.WriteLine(Encode(25638476234, 8));

    }

    public static string Encode(decimal number, int width)

    {

        var nmlOut = new StringBuilder("000000000000000000");

        var letters = new StringBuilder("BCDFGHJKLMNPQRSTVWXZ");

        int lenPrefix;

        int lenSuffix;

        decimal newMin = 0;

        decimal oldMin = 0;

​

        decimal nDistinct = (decimal)Math.Pow(10, width);

        if (width < 1 || width > 18)

        {

            throw new Exception("Not good 1");

        }

        // First determine the length of the alpha prefix and the numeric suffix

        for (lenPrefix = 0, lenSuffix = width; lenPrefix <= width; ++lenPrefix, --lenSuffix)

        {

            oldMin = newMin;

            newMin += nDistinct;

            if (newMin > number)

            {

                // We fit

                break;

            }

            nDistinct *= 2;

        }

        if (lenPrefix > width)

        {

            // Number won't fit

            throw new Exception("Not good 2");

        }

        // offset may contain numbers that are part of the suffix and the prefix

        decimal offset = number - oldMin;

        for (; lenSuffix > 0; lenSuffix--)

        {

            // Now construct the end of the string

            nmlOut[lenPrefix + lenSuffix - 1] = (char)('0' + offset % 10);

            offset /= 10;

        }

​

        for (; lenPrefix > 0; lenPrefix--)

        {

            // Now construct the beginning of the string

            nmlOut[lenPrefix - 1] = letters[(int)(offset % 100) % 20];

            offset /= 20;

        }

        return nmlOut.ToString()[..width];

    }

​

}