using System;

//using System.Collections;

public class Program

{

    public static void Main()

    {

        String s1=Console.ReadLine();

        String s2=Console.ReadLine();

        String s3=s1+s2;

        char[] ch= s3.ToCharArray();

        Array.Sort(ch,StringComparer.Create(new CultureInfo("en-US"),true));

        String result=new String(ch);

        Console.WriteLine(ch);

    }

}