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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.awt.geom.AffineTransform;
import java.io.*;
import java.math.*;
import java.util.*;
public class Main {
	@SuppressWarnings("null")
	public static void main(String[] args) {
		Scanner cin = new Scanner(new BufferedInputStream(System.in));
		String s1 = cin.next();
		String s2 = cin.next();
		int len = s1.length();
		List<Character> a = new ArrayList<Character>();
		List<Character> b = new ArrayList<Character>();
		for(int i = 0; i < len; i++) {
			a.add(s1.charAt(i));
			b.add(s2.charAt(i));
		}
		Collections.sort(a);
		Collections.sort(b);
		Collections.reverse(b);
		int low = 0, high = len-1;
		int l1 = 0, r1 = (a.size() + 1 >> 1) - 1;
		int l2 = 0, r2 = (b.size() >> 1) - 1;
		char []ans = new char[len+3];
		for(int i = 0; i < len; i++) {
			if(i%2 == 0) {
				if(a.get(l1) >= b.get(l2)) {
					ans[high] = a.get(r1);
					r1--;
					high--;
				}
				else {
					ans[low] = a.get(l1);
					l1++;
					low++;
				}
			}
			else {
				if(a.get(l1) >= b.get(l2)) {
					ans[high] = b.get(r2);
					r2--;
					high--;
				}
				else {
					ans[low] = b.get(l2);
					l2++;
					low++;
				}
			}
		}
		for(int i = 0; i < len; i++) {
			System.out.print(ans[i]);
		}
		System.out.println();
//		System.out.println(ans);
	}
}
