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

class Program
{
    static void Main()
    {
        char[] delimeters = new char[] { ' ', ',', '.', '?', '!' };
        string[] textInput = Console.ReadLine().Split(delimeters, StringSplitOptions.RemoveEmptyEntries);

        List<string> palindromes = new List<string>();

        for (int i = 0; i < textInput.Length; i++)
        {
            string firstPart = textInput[i].Substring((textInput[i].Length + 1) / 2);
            char[] getReversed = firstPart.ToCharArray();
            Array.Reverse(getReversed);
            firstPart = new string(getReversed);
            string secondPart = textInput[i].Substring(0, textInput[i].Length / 2);
            if (firstPart == secondPart)
            {
                palindromes.Add(textInput[i]);
            }
        }
        palindromes.Distinct();
        palindromes.Sort();

        Console.WriteLine(string.Join(", ", palindromes));
    }
}