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

namespace YukiCoder
{
    class Program
    {
        static string CheckStr(string S)
        {
            string s="abcdefghijklm";
            var va = s.Where(c => S.IndexOf(c) < 0);
            int n = va.Count();
            if (n == 0) return s;
            if (n == 1) return va.ToArray()[0].ToString();
            return "";
        }


        static void Main(string[] args)
        {
            var S = Console.ReadLine();
            var s = CheckStr(S);
            if (s.Length == 0)          Console.WriteLine("Impossible");
            foreach(char c in s)        Console.WriteLine(c);
            Console.ReadLine();
        }
    }
}