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

class Solution
{
    static void Main()
    {
        var s = Console.ReadLine();
        var remain = new List<char>();

        if(s.Any(c => !"abcdefghijklm".Contains(c)))
        {
            Console.WriteLine("Impossible");
            return;
        }

        foreach (var c in "abcdefghijklm")
        {
            if (!s.Contains(c))
            {
                remain.Add(c);
            }
        }

        if (remain.Count >= 2)
        {
            Console.WriteLine("Impossible");
            return;
        }

        if (remain.Count == 1)
        {
            Console.WriteLine(remain.First());
            return;
        }

        foreach (var c in "abcdefghijklm")
        {
            Console.WriteLine(c);
        }
    }
}