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

bccdb
 z
 dfdeed
 aab
 y
 abac

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

public class CFA {
    public static PrintWriter out;
    public static FastScanner in;

    private void solve() {
        String s1 = in.nextLine();
        String s2 = in.nextLine();

        int n = s1.length();

        Character[] oleg = s1.chars().mapToObj(c->(char)c).toArray(Character[]::new);
        Character[] igor = s2.chars().mapToObj(c->(char)c).toArray(Character[]::new);


        Arrays.sort(oleg);
        Arrays.sort(igor,Collections.reverseOrder());

        int ol = 0, or = n/2-1;
        int il = 0, ir = n/2-1;

        if(n%2 == 1){
            or++;
        }

        Character[] ans = new Character[n];
        int al =0,ar = n-1, chance = 0;
        for(int i=0;i<n;i++){
            if(chance == 0){
                if(oleg[ol] < igor[il]){
                    ans[al++] = oleg[ol++];
                }else {
                    ans[ar--] = oleg[or--];
                }
            }else {
                if(oleg[ol] < igor[il]){
                    ans[al++] = igor[il++];
                }else {
                    ans[ar--] = igor[ir--];
                }
            }
            chance^=1;
        }

        for (int i=0;i<n;i++){
            out.print(ans[i]);
        }

    }

    private void runIO() {
        in = new FastScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out));
        solve();
        out.close();
    }

    private static class FastScanner {
        BufferedReader bufferedReader;
        StringTokenizer stringTokenizer;

        private FastScanner() {
            bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        }

        private String next() {
            if (stringTokenizer == null || !stringTokenizer.hasMoreElements()) {
                try {
                    stringTokenizer = new StringTokenizer(bufferedReader.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return stringTokenizer.nextToken();
        }

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

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

        private String nextLine() {
            String ret = "";
            try {
                ret = bufferedReader.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return ret;
        }
    }

    public static void main(String[] args) {
        new CFA().runIO();
    }
}
