ProblemTwo - DetectiveBoev

using System;
using System.CodeDom;
using System.Linq;
using System.Security.Cryptography;
using System.Text;

internal class ProblemTwo
{
    private static void Main()
    {
        string secretWord = Console.ReadLine();
        int sum = 0;

        for (int i = 0; i < secretWord.Length; i++)
        {
            sum += secretWord[i];

        }
        int value = sum;
        int mask;
        do
        {
            mask = 0;
            while (value > 0)
            {
                mask += value % 10;
                value /= 10;
            }
            value = mask;
        } while (mask >= 10);

        string encryptedMessage = Console.ReadLine();
        byte[] array = Encoding.ASCII.GetBytes(encryptedMessage);
        int[] resultArray = Array.ConvertAll(array, c => (int)c);

        for (int i = 0; i < resultArray.Length; i++)
        {
            if (resultArray[i]%mask==0)
            {
                resultArray[i] += mask;
            }
            else
            {
                resultArray[i] -= mask;
            }
        }

        Array.Reverse(resultArray);

        foreach (var s in resultArray)
        {
            Console.Write(Convert.ToChar(s));
        }

    }

}