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 A {
    public static void main(String[] args) throws Exception {
        FastScanner fs = new FastScanner();
        Scanner s = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        char[] a = s.nextLine().toCharArray();
        char[] b = s.nextLine().toCharArray();
        Arrays.sort(a);
        Arrays.sort(b);
        int p1 = 0, p2 = b.length-1;
        StringBuilder res = new StringBuilder();
        char[] print = new char[a.length];
        int oMoves = a.length / 2 + (a.length%2);
        int iMoves = a.length / 2;
//        System.out.println(iMoves + " " + oMoves);
        int pos = 0, pos2 = 0;
        for(int i = 0; i < a.length; i++) {
            if(i%2==0) {
                if(a[p1] > b[p2]) {
                    pos = find(print, iMoves);
//                    System.out.println("! " + pos);
                } else pos2++;
                print[pos] = a[p1++];
                oMoves--;
                pos++;
            } else {
                if(b[p2] < a[p1]) {
                    pos2 = find(print, oMoves);
                } else pos++;
                print[pos2] = b[p2--];
                iMoves--;
                pos2++;
            }
//            System.out.println("P " + pos + " " + pos2);
        }
        for(int i = 0; i < print.length; i++) {
            if(print[i] == 0) {
                int[] runtime = {1};
                System.out.println(runtime[2]);
            }
            res.append(print[i]);
        }
        out.println(res.toString());

        /*
    zzd
    abc
    ???
         */

        out.close();
    }

    static int find (char[] a, int x) {
        int f = 0;
        for(int i = 0; i < a.length && f <= x; i++) {
            if(a[i] == 0) {
                if(f == x) return i;
                f++;
            }
        }
        return 0;
    }


    static class FastScanner {
        BufferedReader br;
        StringTokenizer st;

        public FastScanner() {
            try	{
                br = new BufferedReader(new InputStreamReader(System.in));
//                br = new BufferedReader(new FileReader("testdata.out"));
                st = new StringTokenizer("");
            } catch (Exception e){e.printStackTrace();}
        }

        public String next() {
            if (st.hasMoreTokens())	return st.nextToken();
            try {st = new StringTokenizer(br.readLine());}
            catch (Exception e) {e.printStackTrace();}
            return st.nextToken();
        }

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

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

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

        public String nextLine() {
            String line = "";
            try {line = br.readLine();}
            catch (Exception e) {e.printStackTrace();}
            return line;
        }

        public Integer[] nextIntegerArray(int n) {
            Integer[] a = new Integer[n];
            for(int i = 0; i < n; i++) a[i] = nextInt();
            return a;
        }

        public int[] nextIntArray(int n) {
            int[] a = new int[n];
            for(int i = 0; i < n; i++) a[i] = nextInt();
            return a;
        }

        public char[] nextCharArray() {
            return nextLine().toCharArray();
        }
    }
}

