public static string RotateRight(this string str, int count)
        {
            if (count >= str.Length)
            {
                count = count - str.Length;
            }

            return str.Substring(str.Length - count, count) + str.Substring(0, str.Length - count);
        }

        public static string RotateLeft(this string str, int count)
        {
            if (count >= str.Length)
            {
                count = count - str.Length;
            }

            return str.Substring(count, str.Length - count) + str.Substring(0, count);
        }

        public static string RotateByLetter(this string str, char letter)
        {
            int count = str.IndexOf(letter);

            if (count >= 4)
            {
                count++;
            }

            return str.RotateRight(count + 1);
        }