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.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

import static java.lang.Math.random;

/**
 * @author Don Li
 */
public class NamingCompany {
    void solve() {
        char[] s = in.nextToken().toCharArray();
        char[] t = in.nextToken().toCharArray();
        int n = s.length;
        
        sort(s);
        sort(t);
        
        int[][] cnt = new int[2][26];
        int ns = (n + 1) / 2, nt = n / 2;
        for (int i = 0; i < ns; i++) cnt[0][s[i] - 'a']++;
        for (int i = n - nt; i < n; i++) cnt[1][t[i] - 'a']++;
        
        int[][] p = new int[2][2];
        p[0][0] = 0;
        while (p[0][0] < 26 && cnt[0][p[0][0]] == 0) p[0][0]++;
        p[0][1] = 25;
        while (p[0][1] >= 0 && cnt[0][p[0][1]] == 0) p[0][1]--;
        p[1][0] = 0;
        while (p[1][0] < 26 && cnt[1][p[1][0]] == 0) p[1][0]++;
        p[1][1] = 25;
        while (p[1][1] >= 0 && cnt[1][p[1][1]] == 0) p[1][1]--;
        
        int fi = 0, se = n - 1;
        char[] res = new char[n];
        for (int i = 0; i < n; i++) {
            if ((i & 1) == 0) {
                if (p[0][0] < p[1][1]) {
                    res[fi++] = (char) (p[0][0] + 'a');
                    cnt[0][p[0][0]]--;
                    while (p[0][0] < 26 && cnt[0][p[0][0]] == 0) p[0][0]++;
                } else {
                    res[se--] = (char) (p[0][1] + 'a');
                    cnt[0][p[0][1]]--;
                    while (p[0][1] >= 0 && cnt[0][p[0][1]] == 0) p[0][1]--;
                }
            } else {
                if (p[1][1] > p[0][0]) {
                    res[fi++] = (char) (p[1][1] + 'a');
                    cnt[1][p[1][1]]--;
                    while (p[1][1] >= 0 && cnt[1][p[1][1]] == 0) p[1][1]--;
                } else {
                    res[se--] = (char) (p[1][0] + 'a');
                    cnt[1][p[1][0]]--;
                    while (p[1][0] < 26 && cnt[1][p[1][0]] == 0) p[1][0]++;
                }
            }
        }
        out.println(new String(res));
    }
    
    void sort(char[] a) {
        int n = a.length;
        for (int i = 0; i < n; i++) {
            int j = (int) (i + random() * (n - i));
            char tmp = a[i];
            a[i] = a[j];
            a[j] = tmp;
        }
        Arrays.sort(a);
    }
    
    public static void main(String[] args) {
        in = new FastScanner(new BufferedReader(new InputStreamReader(System.in)));
        out = new PrintWriter(System.out);
        new NamingCompany().solve();
        out.close();
    }
    
    static FastScanner in;
    static PrintWriter out;
    
    static class FastScanner {
        BufferedReader in;
        StringTokenizer st;
        
        public FastScanner(BufferedReader in) {
            this.in = in;
        }
        
        public String nextToken() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(in.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
        
        public int nextInt() {
            return Integer.parseInt(nextToken());
        }
        
        public long nextLong() {
            return Long.parseLong(nextToken());
        }
        
        public double nextDouble() {
            return Double.parseDouble(nextToken());
        }
    }
}
