using System;
using System.Collections.Generic;
using System.Linq;

namespace _04.Palindromes
{
    public class Program
    {
        public static void Main()
        {
            var text = Console.ReadLine().Split(new char[] { ' ', ',', '.', '?', '!' }, StringSplitOptions.RemoveEmptyEntries);
            var palindromeWords = new List<string>();

            for (int i = 0; i < text.Length; i++)
            {
                if (IsPalindrome(text[i]))
                {
                    palindromeWords.Add(text[i]);
                }
            }
            palindromeWords = palindromeWords.Distinct().ToList();
            Console.WriteLine(string.Join(", ", palindromeWords.OrderBy(p => p)));
        }

        public static bool IsPalindrome(string word)
        {
            var index = word.Length - 1;

            for (int i = 0; i < word.Length / 2; i++)
            {
                if (word[i] != word[index])
                {
                    return false;
                }
                index--;
            }
            return true;
        }
    }
}