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

namespace exercise
{
    class MainClass
    {
        public static void Main()
        {
            string[] text = Console.ReadLine()
                                   .Split(new char[]{' ', ',', '.', '!', '?'},StringSplitOptions.RemoveEmptyEntries);
            Array.Sort(text);
            List<string> result = new List<string>();
            foreach (var word in text)
            {
                if(IsPalindrom(word))
                {
                    if (result.Contains(word))
                    {
                        continue;
                    }
                    result.Add(word);
                }
			}
            Console.WriteLine(String.Join(", ", result));
        }
        public static bool IsPalindrom(string s)
        {
            for (int i = 0; i < s.Length/2; i++)
            {
                if (s[i] != s[s.Length -i -1])
                {
                    return false;
                }
            }
            return true;
        }
    }
}