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

public class Hello
{
    public static void Main()
    {
        var a = "abcdefghijklm";
        var d = new Dictionary<char, int>();
        for (int i = 0; i < 13; i++) d[a[i]] = 0;
        var s = Console.ReadLine().Trim();
        for (int i = 0; i < 13; i++)
            if (d.ContainsKey(s[i])) d[s[i]]++;
            else { Console.WriteLine("Impossible"); goto end; }
        var c1 = d.Count(x => x.Value == 1);
        if (c1 == 13)
            foreach (var x in a) Console.WriteLine(x);
        else if (c1 == 11)
        {
            foreach (var x in d)
                if (x.Value == 0) { Console.WriteLine(x.Key); break; }
        }
        else Console.WriteLine("Impossible");
        end:;
    }
}