public static void Main()
StringBuilder sb = new StringBuilder();
for(var i = 0; i < 2000; i++)
sb.Append("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
string filename = $"f:\\dump\\{filenumber.ToString().PadLeft(8,'0')}.txt";
Console.WriteLine("writing...");
Console.WriteLine(filename);