using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Write a line: ");

        string input = Console.ReadLine();

​

        string[] words = splitLine(input);

​

        if (words.Length == 1) {

            Console.WriteLine("Input at least one word!");

            return;

        }

        Console.WriteLine();

        bool result = false;

        foreach (string word in words) {

            if (checkEquality(word)) {

                result = true;

                Console.Write("{0}\t", word);

            }

        }

        if (!result) {

            Console.WriteLine("There is no matched words :(");

        }

    }

    public static string[] splitLine(string line)

    {

        return Regex.Split(line, @"\W+");

    }

    public static bool checkEquality(string word)

    {

        bool result = false;

        char firstLetter = word[0];

        char lastLetter = word[word.Length - 1];

        if (firstLetter == lastLetter || Math.Abs(firstLetter - lastLetter) == 32) {

            result = true;

        }

        return result;

    }

}