Задача по С#

 internal class Program 
{ 
    static void Main(string[] args) 
    { 
        Console.WriteLine(Caesar.Crypt(Console.ReadLine(), int.Parse(Console.ReadLine()))); 
    } 
} 
 
static class Caesar 
{ 
    private static string Alphabet; 
 
    private static void BuildAlphabet() 
    { 
        Alphabet = string.Empty; 
        for (char c = 'A'; c <= 'Z'; c++) 
            Alphabet += c.ToString(); 
    } 
 
    static Caesar() 
    { 
        BuildAlphabet(); 
    } 
 
    public static string Crypt(string _CryptoString, int _Shift) 
    { 
        string Result = string.Empty; 
        var Chars = _CryptoString.ToUpper().ToCharArray(); 
        int PositiveShift = Math.Abs(_Shift) / Alphabet.Length + 2; 
        foreach (char c in Chars)  
        { 
            char CryptoChar = c; 
            int Pos = Alphabet.IndexOf(CryptoChar); 
            if (Pos >= 0) 
                CryptoChar = Alphabet[(Pos + _Shift + PositiveShift * Alphabet.Length) % Alphabet.Length]; 
            Result += CryptoChar; 
        } 
        return Result; 
    } 
}