Problem 2 – Detective Boev

using System;
using System.Collections;
class Program
{
    static void Main()
    {
        string secretWord = Console.ReadLine();
        string encryptedMessage = Console.ReadLine();
        int result = 0;
        int mask = 0;

        foreach (char c in secretWord)
        {
            if (c > 0 || c <= 99)
            {
                mask += c % 10 + c / 10;
            }
            else if (c >= 100 || c <= 999)
            {
                int edinici = c % 10;
                int desetici = (c - (c % 10)) / 100;
                int stotici = c / 100;
                mask += edinici + desetici + stotici;
            }
        }
        for (int i = 0; i < encryptedMessage.Length; i++)
        {
            foreach (char a in encryptedMessage)
            {
                result += a;
                if (i % mask == 0)
                {
                    result += mask;
                }
                else
                {
                    result -= mask;
                }
            }
        }
        Console.WriteLine(Convert.ToChar(result));
    }
}