123

   Console.WriteLine("Введи строку:");
            char[] a = Console.ReadLine().ToCharArray();
            var letters = new List<char>();
            var nonLetters = new List<char>();
            string str = new string(a);
            string[] words = str.Split(new char[] { ' ' },StringSplitOptions.RemoveEmptyEntries);
            StringBuilder sb = new StringBuilder(str.Length);
            foreach (string s in words)
            {
                foreach (var i in s)
                {
                    if (char.IsLetter(i))
                    {

                        letters.Add(i);

                        letters.Insert(0, i);
                        Console.Write(i);
                    }
                    else if (char.IsNumber(i))
                    {
                        nonLetters.Add(i);
                    }
                    else
                    {


                    }
                }
                // const string separator = " ";
                // String s1 = String.Join(separator, a);
              //  Console.Write(new string(s.Reverse().ToArray()));
                Console.Write(' ');
                // String s1 = String.Join(" ", s);
                // Console.Write(letters);
                // letters.Reverse(i);
                // letters =new List <char>.Reverse(i ,5);
                //  for (int j = s.Length; j-- != 0;)

                //    sb.Append(str);
                //  Console.Write(sb);

            }
            Console.ReadKey();