string s = Console.ReadLine();

        //s.Replace("+", "");
        string valo = string.Empty;

        var c = s.ToCharArray();

        Array.Sort(c);

        for (int i = 0; i < c.Length; i++)
        {
            if (Char.IsDigit(c[i]))
            {
                valo += c[i];
                valo += "+";
            }
        }
        Console.WriteLine(valo.Substring(0, valo.Length - 1));
}