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

class No548
{
    static void Main()
    {
        var str = Console.ReadLine().OrderBy(x => x);
        var count = str.Distinct().Count();
        char[] strArray = new char[] { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm' };
        List<char> ansList = new List<char>();
        if (count < 12)
        {
            Console.WriteLine("Impossible");
            return;
        }
        else if (count == 12)
        {
            for (int i = 0; i < 13; ++i)
            {
                if (!str.Contains(strArray[i]))
                {
                    ansList.Add(strArray[i]);
                    break;
                }
            }
        }
        else
        {
            ansList.AddRange(strArray);
        }
        foreach (var ans in ansList)
        {
            Console.WriteLine(ans);
        }
    }
}