using System;

using System.Linq;

using System.Text;

public class Program

{

    public static void Main()

    {

    }

         public static string FlipWords(string input)

        {

            var result = new StringBuilder();

            var word = new StringBuilder();

            foreach (char letter in input)

            {

                if (_separators.Contains(letter))

                {

                    StringBuilder reversed = ReverseString(word);

                    result.Append(reversed);

                    result.Append(letter);

                    word = new StringBuilder();

                }

                else

                {

                    word.Append(letter);

                }

            }

            return result.ToString();

        }

​

        public static StringBuilder ReverseString(StringBuilder input)

        {

            var result = new StringBuilder();

            for (var i = 0; i < input.Length; i++)

            {

                int index = input.Length - i - 1;

                result.Append(input[index]);

            }

            return result;

        }

}