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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.*;
import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.*;
import java.io.IOException;
import java.io.InputStream;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class Main {
    public static void main(String[] args) {

        File file = new File("in.txt");
        File fileOut = new File("out.txt");
        InputStream inputStream = null;
        OutputStream outputStream = null;
        // try {inputStream= new FileInputStream(file);} catch (FileNotFoundException ex){return;};
//        try {outputStream= new FileOutputStream(fileOut);} catch (FileNotFoundException ex){return;};
        inputStream = System.in;
        outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Task solver = new Task();
        solver.solve(1, in, out);
        out.close();
    }


}

class Task {

    public void solve(int testNumber, InputReader in, PrintWriter out) {
        String min = in.next();
        String max = in.next();

        LinkedList<Character> qmin = new LinkedList<>();
        LinkedList<Character> qmax = new LinkedList<>();

        for(int i=0; i<min.length(); i++){
            qmin.add(min.charAt(i));
            qmax.add(max.charAt(i));
        }

        qmin.sort(Comparator.naturalOrder());
        qmax.sort(Comparator.reverseOrder());

        if(min.length() % 2 == 0){
            qmin.subList(min.length()/2, min.length()).clear();
            qmax.subList(min.length()/2, min.length()).clear();
        }
        else{
            qmin.subList(min.length()/2+1, min.length()).clear();
            qmax.subList(min.length()/2, min.length()).clear();

        }


        char[] result = new char[min.length()];
        Integer firstFree = 0;
        Integer lastFree = min.length()-1;
        for(int i=0; i<min.length(); i++){
            if(i%2==0){ // Oleg turn
                if(qmin.size()>0 && qmax.size()>0 && qmin.peek() >= qmax.peek()){
                    result[lastFree] = qmin.pollLast();
                    lastFree--;
                }
                else{
                    result[firstFree] = qmin.pollFirst();
                    firstFree++;
                }
            }
            else{
                if(qmin.size()>0 && qmax.size()>0 && qmin.peek() >= qmax.peek()){
                    result[lastFree] = qmax.pollLast();
                    lastFree--;
                }
                else{
                    result[firstFree] = qmax.pollFirst();
                    firstFree++;
                }
            }
        }
        for(int i=0; i<min.length(); i++){
            out.print(result[i]);
        }
        out.println();

    }


}



class InputReader {
    public BufferedReader reader;
    public StringTokenizer tokenizer;

    public InputReader(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream), 32768);
        tokenizer = null;
    }

    public String next() {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

    public String nextLine(){
        try {
            return reader.readLine();
        } catch (IOException e){
            throw new RuntimeException(e);
        }
    }

    public int nextInt() {
        return Integer.parseInt(next());
    }
    public long nextLong() { return Long.parseLong(next()); }

}



class Pair<F, S> {
    public final F first;
    public final S second;




    public Pair(F first, S second) {
        this.first = first;
        this.second = second;
    }

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof Pair)) {
            return false;
        }
        Pair<?, ?> p = (Pair<?, ?>) o;
        return Objects.equals(p.first, first) && Objects.equals(p.second, second);
    }

    @Override
    public int hashCode() {
        return (first == null ? 0 : first.hashCode()) ^ (second == null ? 0 : second.hashCode());
    }

    @Override
    public String toString() {
        return "(" + first + ", " + second + ')';
    }
}

class IntPair extends Pair<Integer, Integer>{
    public IntPair(Integer first, Integer second){
        super(first, second);
    }
}