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.DataInputStream;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;

public class Main {
	
	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		
		ArrayList<Character> small = new ArrayList<Character>();
		ArrayList<Character> large = new ArrayList<Character>();
		
		String s = sc.nextLine();
		int n = s.length();
		for(int i = 0; i < n; ++i) small.add(s.charAt(i));
		Collections.sort(small);
		s = sc.nextLine();
		for(int i = 0; i < n; ++i) large.add(s.charAt(i));
		Collections.sort(large, Collections.reverseOrder());
		
		StringBuilder sb = new StringBuilder();
		int j = 0, k = 0;
		
		int i;
		Stack<Character> st = new Stack<Character>();
		
		for(i = 0; i < n; ++i) {
			if((i & 1) == 0) {
				if(small.get(j) > large.get(k))
					st.add(small.get(j++));
				else
					sb.append(small.get(j++));
			}
			else {
				if(small.get(j) > large.get(k))
					st.add(large.get(k++));
				else
					sb.append(large.get(k++));
			}
		}
		
		while(!st.isEmpty()) sb.append(st.pop());
		
		out.println(sb.toString());
		
		out.flush();
		out.close();
	}

	static class Pair implements Comparable<Pair> {
		int a, b;
		
		public Pair(int x, int y) {
			a = x;
			b = y;
		}
		
		@Override
		public int compareTo(Pair p) {
			return p.b - b;
		}
		
		@Override
		public String toString() {
			return a + " " + b;
		}
	}
	
	static class Scanner{
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}

		public Scanner(FileReader r){	br = new BufferedReader(r);}

		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 double nextDouble() throws IOException { return Double.parseDouble(next()); }

		public boolean ready() throws IOException {return br.ready();}
	}
}