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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.*;
import java.util.Collections;
import java.util.PriorityQueue;
import java.util.StringTokenizer;

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

    private void solve() {
        String oleg = in.nextLine();
        String igor = in.nextLine();

        PriorityQueue<Character> og = new PriorityQueue<>();
        PriorityQueue<Character> ir = new PriorityQueue<>(Collections.reverseOrder());

        int n = oleg.length();
        for(int i=0;i<n;i++){
            og.add(oleg.charAt(i));
        }

        for(int i=0;i<n;i++){
            ir.add(igor.charAt(i));
        }

        char[] ans = new char[n+1];
        int chance = 0;

        int i;
        for(i=1;i<=n;i++){
            char a = og.peek();
            char b = ir.peek();

            if(chance == 0){
                if(a < b){
                    ans[i] = a;
                }else break;
                og.poll();
            }else{
                if(b > a){
                    ans[i] = b;
                }else break;
                ir.poll();
            }
            chance^=1;
        }

        int p = n-i+1;
        if(p > 0){
            if(p%2 != 0){
                if(chance == 0){
                    ans[i++] = og.poll();
                }else ans[i++] = ir.poll();
                chance^=1;
            }

            int j = i;
            for(;j<=n;j+=2){
                if(chance == 1) {
                    ans[j] = og.poll();
                }else{
                    ans[j] = ir.poll();
                }
            }
            j = i+1;
            for(;j<=n;j+=2){
                if(chance == 0) {
                    ans[j] = og.poll();
                }else{
                    ans[j] = ir.poll();
                }
            }
        }

        for(i=1;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();
    }
}
