bcdef
abbbc
 z
y
 reddit
abcdef
 abc
aaa
 y
z
 cbxz
aaaa

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class NamingCompany {
	public static int OlegLetters[] = new int[26];
	public static int IgorLetters[] = new int[26];
	public static char getLeast()
	{
		for (int i=0;i<26;i++)
		{
			if (OlegLetters[i]>0)
			{
				OlegLetters[i]--;
				return ((char) (i+'a'));
			}
		}
		return 'a';
	}
	public static char getMost()
	{
		for (int i=25;i>0;i--)
		{
			if (IgorLetters[i]>0)
			{
				IgorLetters[i]--;
				return ((char) (i+'a'));
			}
		}
		return 'a';
	}
	public static void main(String args[]) throws IOException
	{
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		String Oleg = sc.nextLine();
		String Igor = sc.nextLine();
		int n = Oleg.length();
		for (int i=0;i<n;i++)
		{
			int c = Oleg.charAt(i);
			OlegLetters[c-'a']++;
			c = Igor.charAt(i);
			IgorLetters[c-'a']++;
		}
		boolean OlegTurn = true;
		for (int i=0;i<n;i++)
		{
			pw.print(OlegTurn?getLeast():getMost());
			OlegTurn  = !OlegTurn;
		}
		pw.println();
		pw.flush();
		pw.close();
	}
	static class Scanner 
	{
		StringTokenizer st;
		BufferedReader br;
	
		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}
	
		public String next() throws IOException 
		{
			while (st == null || !st.hasMoreTokens()) 
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
	
		public int nextInt() throws IOException {return Integer.parseInt(next());}
		
		public long nextLong() throws IOException {return Long.parseLong(next());}
	
		public String nextLine() throws IOException {return br.readLine();}
		
		public boolean ready() throws IOException {return br.ready();}
	
	
	}
}
