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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.List;
import java.util.Scanner;
import java.util.Collections;
import java.util.ArrayList;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        int size = 0;
        char[] res;

        public void solve(int testNumber, Scanner in, PrintWriter out) {
            List<Character> a = new ArrayList<>();
            List<Character> b = new ArrayList<>();
            String s = in.next();
            size = s.length();
            for (char c : s.toCharArray()) a.add(c);
            s = in.next();
            for (char c : s.toCharArray()) b.add(c);
            Collections.sort(a);
            Collections.sort(b, Collections.reverseOrder());
            a = a.subList(0, size / 2 + (size % 2));
            b = b.subList(0, size / 2);
            Collections.reverse(b);
            res = new char[size];
            int t = 0, ip = 0, it = size - 1, ap = 0, at = a.size() - 1, bp = 0, bt = b.size() - 1;
            while (ip <= it) {
                if (t % 2 == 0) {
                    if (bp > bt || a.get(ap) < b.get(bt)) {
                        res[ip] = a.get(ap);
                        ap++;
                        ip++;
                    } else {
                        res[it] = a.get(at);
                        at--;
                        it--;
                    }
                } else {
                    if (ap > at || b.get(bt) > a.get(at)) {
                        res[ip] = b.get(bt);
                        bt--;
                        ip++;
                    } else {
                        res[it] = b.get(bp);
                        bp++;
                        it--;
                    }
                }
                t = 1 - t;
            }
            out.print(new String(res));
        }

    }
}

