var poly = File.ReadAllText(Path.Combine(Path.GetDirectoryName(Util.CurrentQueryPath), @"05_input.txt")).Trim(); for (;;) { var len = poly.Length; for (var i='a';i<='z';i++) poly=poly.Replace(i+""+char.ToUpper(i), ""); for (var i='a';i<='z';i++) poly=poly.Replace(char.ToUpper(i)+""+i, ""); if (len == poly.Length) { poly.Length.Dump(); return; } }