class Program
{

    internal static string CreateString(int stringLength)
    {
        Random rd = new Random();
        const string allowedChars = "ABCDEFGHJKLMNOPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz0123456789!@$?_-";
        char[] chars = new char[stringLength];

        for (int i = 0; i < stringLength; i++)
        {
            chars[i] = allowedChars[rd.Next(0, allowedChars.Length)];
        }

        return new string(chars);
    }

    static Dictionary<char, int> CountCharsInStr(string str)
    {
        return str
            .Where(c => ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')))
            .GroupBy(char.ToLower)
            .ToDictionary(g => g.Key, g => g.Count());
    }

    static void Main(string[] args)
    {
        string[] strings = new string[1000];
        for (int i = 0; i < 1000; i++)
        {
            strings[i] = CreateString(10000);
        }


        var watch = System.Diagnostics.Stopwatch.StartNew();
        for (int i = 0; i < 1000; i++)
        {
            CountCharsInStr(strings[i]);
        }
        watch.Stop();
        var elapsedMs = watch.ElapsedMilliseconds;
        Console.WriteLine(elapsedMs);
    }
}