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);
            List<Integer> is = new ArrayList<>();
            for (int i = 0; i < size; i++)
                is.add(i);
            res = new char[size];
            int t = 0, aptr = 0, bptr = 0, iptr = 0, aptr2 = a.size() - 1, bptr2 = b.size() - 1, iptr2 = is.size() - 1;
            while (iptr <= iptr2) {
                if (t % 2 == 0) {
                    if (bptr == bptr2 || aptr >= 0 && bptr2 >= 0 && a.get(aptr) < b.get(bptr2)) {
                        res[iptr] = a.get(aptr);
                        aptr++;
                        iptr++;
                    } else {
                        res[iptr2] = a.get(aptr2);
                        aptr2--;
                        iptr2--;
                    }
                } else {
                    if (aptr == aptr2 || bptr2 >= 0 && aptr2 >= 0 && b.get(bptr2) > a.get(aptr2)) {
                        res[is.get(iptr)] = b.get(bptr2);
                        bptr2--;
                        iptr++;
                    } else {
                        res[is.get(iptr2)] = b.get(bptr);
                        bptr++;
                        iptr2--;
                    }
                }
                t = 1 - t;
            }
            out.print(new String(res));
        }

    }
}

