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

namespace No256
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			var n = Console.ReadLine ();
			var array = n.ToCharArray ();
			Array.Sort (array);
			Array.Reverse (array);

			foreach (var element in array) {
				Console.Write (element);
			}
			Console.WriteLine ();
		}
	}
}