2. Decoding

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

class Program
{
    static void Main()
    {
        Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
        int salt = int.Parse(Console.ReadLine());
        string input = Console.ReadLine();

        for (int i = 0; i < input.Length; i++)
        {
            if (input[i] == '@')
            {
                break;
            }
            if (Char.IsLetter(input[i]))
            {
                double number = (int)(input[i])*salt + 1000;
                if (i%2 == 0)
                {
                    double decodedNumber = number/100;
                    Console.WriteLine("{0:F2}", decodedNumber);
                }
                else
                {
                    double decodedNumber = number * 100;
                    Console.WriteLine("{0}", decodedNumber);
                }
            }
            else if (Char.IsDigit(input[i]))
            {
                double number = (int)(input[i]) + salt + 500;
                if (i % 2 == 0)
                {
                    double decodedNumber = number / 100;
                    Console.WriteLine("{0:F2}", decodedNumber);
                }
                else
                {
                    double decodedNumber = number * 100;
                    Console.WriteLine("{0}", decodedNumber);
                }
            }
            else
            {
                double number = (int)(input[i])  - salt;
                if (i % 2 == 0)
                {
                    double decodedNumber = number / 100;
                    Console.WriteLine("{0:F2}", decodedNumber);
                }
                else
                {
                    double decodedNumber = number * 100;
                    Console.WriteLine("{0}", decodedNumber);
                }
            }
        }

    }
}