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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.*;
import java.math.*;
import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner cin = new Scanner(new BufferedInputStream(System.in));
		String a = cin.next();
		String b = cin.next();
		int len = a.length();
		char []s1 = new char[len];
		char []s2 = new char[len];
		for(int i = 0; i < len; i++) {
			s1[i] = a.charAt(i);
			s2[i] = b.charAt(i);
		}
		Arrays.sort(s1);
		Arrays.sort(s2);
//		System.out.println(s1);
//		System.out.println(s2);
		int idx1 = 0, idx2 = len - 1;
		char []ans = new char[len];
		for(int i = 0; i < len; i++) {
			if(i % 2 == 0) {
				if(ans[i] != 0) ans[i-1] = s1[idx1];
				else if(i == len-1) ans[i] = s1[idx1];
				else if(s1[idx1] >= s2[idx2]) ans[i+1] = s1[idx1];
				else ans[i] = s1[idx1];
				idx1++;
			}
			else {
				if(ans[i] != 0) ans[i-1] = s2[idx2];
				else if(i == len-1) ans[i] = s2[idx2];
				else if(s2[idx2] > s1[idx1]) ans[i] = s2[idx2];
				else ans[i+1] = s2[idx2];
				idx2--;
			}
		}
		System.out.println(ans);
	}
}
