using System;
using System.Linq;

class No587
{
    static void Main()
    {
        var str = Console.ReadLine();
        var count = 0;
        var ans = "";
        foreach (var c in str)
        {
            if (c != 0)
            {
                str.Remove(c);
                if (str.Contains(c))
                {
                    str.Replace(c, '0');
                    count++;
                }
                else ans = c.ToString();
            }
        }
        Console.WriteLine(count == 6 ? ans : "Impossible");
    }
}