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.Arrays;
import java.util.Comparator;
import java.util.StringTokenizer;

public class Abood3A {


	public static void main(String[] args) throws Exception{

		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		
		String A = sc.next();
		Character[] a = new Character[A.length()];
		
		for (int i = 0; i < a.length; i++) {
			a[i] = A.charAt(i);
		}
		String B = sc.next();
		Character[] b = new Character[A.length()];
		for (int i = 0; i < a.length; i++) {
			b[i] = B.charAt(i);
		}
		Arrays.sort(a);
		Arrays.sort(b, new Comparator<Character>() {

			@Override
			public int compare(Character o1, Character o2) {
				return o2 - o1;
			}
		});
		int i = 0;
		int j = a.length - 1;
		char[] ans = new char[j + 1];
		
		int p1 = 0;
		int p2 = 0;
		while(i < a.length - 1) {
			if(a[p1] < b[p2]) {
				ans[i] = a[p1];
				ans[i + 1] = b[p2];
			}else {
				ans[i] = b[p2];
				ans[i + 1] = a[p1];
			}
			
			p1++;
			p2++;
			i += 2;
		}
		
		if(a.length % 2 == 1)
			ans[a.length - 1] = a[p1];
		for (int k = 0; k < ans.length; k++) {
			out.print(ans[k]);
		}
		out.println();
		
		out.flush();
		out.close();
	}


	static class Scanner 
	{
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream System){br = new BufferedReader(new InputStreamReader(System));}
		public String next() throws IOException 
		{
			while (st == null || !st.hasMoreTokens()) 
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
		public String nextLine()throws IOException{return br.readLine();}
		public int nextInt() throws IOException {return Integer.parseInt(next());}
		public double nextDouble() throws IOException {return Double.parseDouble(next());}
		public char nextChar()throws IOException{return next().charAt(0);}
		public Long nextLong()throws IOException{return Long.parseLong(next());}
		public boolean ready() throws IOException{return br.ready();}
		public void waitForInput(){for(long i = 0; i < 3e9; i++);}
	}
}