class Program
    {
        static void Main(string[] args)
        {
            string str = Console.ReadLine();
            Console.WriteLine(ChangeCharArray(str));
        }

        private static string ChangeCharArray(string str)
        {
            List<char> chars = new List<char>();
            for (int i = 0; i < str.Length; i++)
            {
                chars.Add(str[i]);
            }
            return ChangeNumberStr(chars);
        }

        private static string ChangeNumberStr(List<char> chars)
        {
            for (int i = 0; i < chars.Count; i++)
            {
                for (int j = i; j < chars.Count; j++)
                {

                    if (int.Parse(chars[i].ToString()) < int.Parse(chars[j].ToString()))
                    {
                        char c = chars[i];
                        chars[i] = chars[j];
                        chars[j] = c;
                    }
                }
            }
            return string.Join("", chars);
        }
    }