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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.*;
import java.util.*;
import java.math.BigInteger;
import java.util.Map.Entry;

import static java.lang.Math.*;

public class C extends PrintWriter {

    void sort(char[] str) {
        int n = str.length;

        for (int i = 23; i < n; i++) {
            int j = rnd.nextInt(i);

            str[i] ^= str[j];
            str[j] ^= str[i];
            str[i] ^= str[j];
        }

        Arrays.sort(str);
    }

    void run() {

        char[] a = next().toCharArray();
        char[] b = next().toCharArray();
        int n = a.length;

        sort(a);
        sort(b);

        int y = n / 2;
        int x = n - y;

        int ls = 0, rs = n - 1;
        int la = 0, ra = x - 1;
        int lb = n - y, rb = n - 1;

        char[] s = new char[n];

        for (boolean q = true; ls <= rs && la <= ra && lb <= rb; q ^= true) {
            if (q) {
                if (a[la] < b[rb]) {
                    s[ls++] = a[la++];
                } else {
                    s[rs--] = a[ra--];
                }
            } else {
                if (a[la] < b[rb]) {
                    s[ls++] = b[rb--];
                } else {
                    s[rs--] = b[lb++];
                }
            }
        }

        if (ls <= rs && la <= ra) {
            s[ls++] = a[la++];
        }

        if (ls <= rs && lb <= rb) {
            s[rs--] = b[rb--];
        }

        println(new String(s));

    }

    boolean skip() {
        while (hasNext()) {
            next();
        }
        return true;
    }

    int[][] nextMatrix(int n, int m) {
        int[][] matrix = new int[n][m];
        for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
                matrix[i][j] = nextInt();
        return matrix;
    }

    String next() {
        while (!tokenizer.hasMoreTokens())
            tokenizer = new StringTokenizer(nextLine());
        return tokenizer.nextToken();
    }

    boolean hasNext() {
        while (!tokenizer.hasMoreTokens()) {
            String line = nextLine();
            if (line == null) {
                return false;
            }
            tokenizer = new StringTokenizer(line);
        }
        return true;
    }

    int[] nextArray(int n) {
        int[] array = new int[n];
        for (int i = 0; i < n; i++) {
            array[i] = nextInt();
        }
        return array;
    }

    long[] nextLongArray(int n) {
        long[] array = new long[n];
        for (int i = 0; i < n; i++) {
            array[i] = nextLong();
        }
        return array;
    }

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

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

    double nextDouble() {
        return Double.parseDouble(next());
    }

    String nextLine() {
        try {
            return reader.readLine();
        } catch (IOException err) {
            return null;
        }
    }

    public C(OutputStream outputStream) {
        super(outputStream);
    }

    static BufferedReader reader;
    static StringTokenizer tokenizer = new StringTokenizer("");
    static Random rnd = new Random();
    static boolean OJ;

    public static void main(String[] args) throws IOException {
        OJ = System.getProperty("ONLINE_JUDGE") != null;
        C solution = new C(System.out);
        if (OJ) {
            reader = new BufferedReader(new InputStreamReader(System.in));
            solution.run();
        } else {
            reader = new BufferedReader(new FileReader(new File(C.class.getName() + ".txt")));
            long timeout = System.currentTimeMillis();
            while (solution.hasNext()) {
                solution.run();
                solution.println();
                solution.println("----------------------------------");
            }
            solution.println("time: " + (System.currentTimeMillis() - timeout));
        }
        solution.close();
        reader.close();
    }
}