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

class Program
{
    public void Solve()
    {
        string N = Console.ReadLine();
        char[] aryN = N.ToCharArray();

        Array.Sort(aryN);
        Array.Reverse(aryN);

        Console.WriteLine(new string(aryN));
    }

    static void Main()
    {
        var solver = new Program();
        solver.Solve();
    }
}