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

bccdb
 z
 dfdeed
 aab
 y
 abac

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

public class A implements Runnable {

    public void run() {
        long startTime = System.nanoTime();

        char[] a = nextToken().toCharArray();
        char[] b = nextToken().toCharArray();

        int n = a.length;

        Arrays.sort(a);
        Arrays.sort(b);

        int z = n + 1 >> 1;
        int ai = 0, aj = z - 1;
        int bi = z, bj = n - 1;

        char[] c = new char[n];
        int fi = 0, fj = n - 1;

        for (int it = 0; it < n; it++) {
            if (it % 2 == 0) {

                if (a[ai] < b[bj]) {
                    c[fi++] = a[ai++];
                } else {
                    c[fj--] = a[aj--];
                }

            } else {

                if (b[bj] > a[ai]) {
                    c[fi++] = b[bj--];
                } else {
                    c[fj--] = b[bi++];
                }

            }
        }

        println(new String(c));

        if (fileIOMode) {
            System.out.println((System.nanoTime() - startTime) / 1e9);
        }
        out.close();
    }

    //-----------------------------------------------------------------------------------

    private static boolean fileIOMode;
    private static String problemName = "a";
    private static BufferedReader in;
    private static PrintWriter out;
    private static StringTokenizer tokenizer;

    public static void main(String[] args) throws Exception {
        fileIOMode = args.length > 0 && args[0].equals("!");
        if (fileIOMode) {
            in = new BufferedReader(new FileReader(problemName + ".in"));
            out = new PrintWriter(problemName + ".out");
        } else {
            in = new BufferedReader(new InputStreamReader(System.in));
            out = new PrintWriter(System.out);
        }
        tokenizer = new StringTokenizer("");

        new Thread(new A()).start();
    }

    private static String nextLine() {
        try {
            return in.readLine();
        } catch (IOException e) {
            return null;
        }
    }

    private static String nextToken() {
        while (!tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(nextLine());
        }
        return tokenizer.nextToken();
    }

    private static int nextInt() {
        return Integer.parseInt(nextToken());
    }

    private static long nextLong() {
        return Long.parseLong(nextToken());
    }

    private static double nextDouble() {
        return Double.parseDouble(nextToken());
    }

    private static BigInteger nextBigInteger() {
        return new BigInteger(nextToken());
    }

    private static void print(Object o) {
        if (fileIOMode) {
            System.out.print(o);
        }
        out.print(o);
    }

    private static void println(Object o) {
        if (fileIOMode) {
            System.out.println(o);
        }
        out.println(o);
    }

    private static void printf(String s, Object... o) {
        if (fileIOMode) {
            System.out.printf(s, o);
        }
        out.printf(s, o);
    }
}
