Secret_Number

using System;

class SecretNumber
{
    static void Main()
    {
        string N = Console.ReadLine();

        int specialSum = 0;

        char[] myArr = new char[N.Length - 1];
        if (N[0] == '-')
        {
            for (int i = 0; i < N.Length - 1; i++)
            {
                myArr[i] = N[i + 1];
            }
            N = new string(myArr);
        }


        int count = 0;
        int value = 0;

        for (int i = N.Length - 1; i >= 0; i--)
        {
            count++;
            value = int.Parse(N[i].ToString());
            if (count % 2 == 1)
            {
                specialSum += value * (int)Math.Pow(count, 2);
            }
            else
            {
                specialSum += (int)Math.Pow(value,2) * count;
            }
        }

        Console.WriteLine(specialSum);

        int lastDigit = 0;
        lastDigit = specialSum % 10;
        int R = specialSum % 26 + 1;

        char letter = '\0';
        int next = R - 1;

        if (lastDigit == 0)
        {
            Console.WriteLine("{0} has no secret alpha-sequence", N);
        }
        else
        {
            for (int i = 0; i < lastDigit; i++)
            {
                letter = (char)(65 + next);
                Console.Write("{0}", letter);
                next++;
                if (letter == 'Z')
                {
                    next = 0;
                }
            }
        }

        Console.WriteLine();
    }
}