using System;
using System.IO;
using System.Linq;

namespace ACMPC
{
    class Program
    {
        static void Main(string[] args)
        {
            try {
                FilterFile(args.Length>0?new StreamReader(args[0]):Console.In,
                    args.Length>1?new StreamWriter(args[1]):Console.Out);
            } catch(IOException e)
            {
                Console.Error.WriteLine("IO error encountered: {0}", e.Message);
            }
        }
        static readonly string validChars = "abcdefghijklmnopqrstuvwxyz ";
        static void FilterFile(TextReader input, TextWriter output)
        {
            string val = null;
            while ((val = input.ReadLine().ToLower()) != "end")
                if (!val.Any(x => !validChars.Contains(x)||
                    (x!=' ' && val.Where(y => y == x).Count() > 1)))
                    output.WriteLine(val);
        }
    }
}