Program.cs

static void Main(string[] args)
{
    var zipCodes = new List<int>();
    var letter = new Letter();
    for (int index = 0; index < 23458333; index++)
    {
        zipCodes.Add(index % 100000);
        string pieceStatistics = letter.GetStatistics(zipCodes[index]);
        Console.Write(pieceStatistics);
    }

    Console.ReadLine();
}