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

bccdb
 z
 dfdeed
 aab
 y
 abac

/*
 * Author Ayub Subhaniya
 * Institute DA-IICT
 */

import java.io.*;
import java.math.*;
import java.util.*;


public class Codeforces408 {
	
	InputStream in;
	PrintWriter out;
	
	void solve() 
	{
		char []c1=ns().toCharArray();
		char []c2=ns().toCharArray();
		int n=c1.length;
		char []c=new char[n];
		
		Arrays.sort(c1);
		Arrays.sort(c2);
		//tr(c1);
		//tr(c2);
		
		int c1s=0,c1e=(n-1)/2;
		int c2s=n-1,c2e=c2s-n/2+1;
		
		int start=0,end=n-1;
		
		boolean flag=false;
		if (n%2!=0)
		{
			flag=true;
			n--;
		}
			
		
		for (int size=0;size<n;size++)
		{
			//tr(c);
			//tr(start+"-"+end);
			//tr("1->"+c1s+"-"+c1e);
			//tr("2->"+c2s+"-"+c2e);
			
			if (size%2==0)
			{
				if (c1[c1s]>=c2[c2s])
				{
					c[end--]=c1[c1e--];
				}
				else
				{
					c[start++]=c1[c1s++];
				}
			}
			else
			{
				if (c1[c1s]>=c2[c2s])
				{
					c[end--]=c2[c2e++];
				}
				else
				{
					c[start++]=c2[c2s--];
				}
			}
		}
		
		if (flag)
		{
			c[start++]=c1[c1e++];
			n++;
		}
		
		for (int i=0;i<n;i++)
			out.print(c[i]);
	}

	void run() throws Exception {
		String INPUT = "C:/Users/ayubs/Desktop/input.txt";
		//oj=true;
		in = oj ? System.in : new FileInputStream(INPUT);
		out = new PrintWriter(System.out);
		
			long s = System.currentTimeMillis();
			solve();
			out.flush();
			tr(System.currentTimeMillis() - s + "ms");
		
	}
	public static void main(String[] args) throws Exception {
		new Codeforces408().run();
	}
	
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	
	private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = in.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private boolean inSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	}
	
	private int skip() {
		int b;
		while ((b = readByte()) != -1 && inSpaceChar(b))
			;
		return b;
	}
	
	private double nd() {
		return Double.parseDouble(ns());
	}
	
	private char nc() {
		return (char) skip();
	}
	
	private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(inSpaceChar(b))) { // when nextLine, (inSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n && !(inSpaceChar(b))) {
			buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}
	
	private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}
	
	private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		
		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		
		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private boolean oj = System.getProperty("ONLINE_JUDGE") != null;
	
	private void tr(Object... o) {
		if (!oj)
			System.out.println(Arrays.deepToString(o));
	}
}
