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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.*;

public class CTask {


    public static void main(String[] args) throws IOException {
        MyInputReader in = new MyInputReader(System.in);
        char[] s1 = in.next().toCharArray();
        char[] s2 = in.next().toCharArray();
        int[] a = new int[27];
        int[] b = new int[27];
        for (int i = 0; i < s1.length; i++) {
            a[s1[i] - 'a'] += 1;
            b[s2[i] - 'a'] += 1;
        }
        char[] result = new char[s1.length];
        int left = 0;
        int right = 27 - 1;
        boolean flag = true;
        int cnt = 0;
        boolean f = true;
        for (int i = 0; i < s1.length; i++) {
            while (a[left] <= 0) {
                left++;
            }
            while (b[right] <= 0) {
                right--;
            }
            if (left >= right && f) {
                f = false;
                if ((s1.length - i) % 2 == 0) {
                    flag = !flag;
                }
            }
            if (flag) {
                result[i] = (char) (left + 'a');
                a[left] -= 1;
            } else {
                result[i] = (char) (right + 'a');
                b[right] -= 1;
            }
            flag = !flag;
            cnt += 1;
        }
        if (!f) {

        }
        for (int i = 0; i < s1.length; i++) {
            System.out.print(result[i]);
        }
    }


    static class MyInputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

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

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

    }

}