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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskC {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            String s = in.next();
            String t = in.next();
            int[] sCnt = new int[26];
            int[] tCnt = new int[26];
            for (int i = 0; i < s.length(); i++) {
                sCnt[s.charAt(i) - 'a']++;
                tCnt[t.charAt(i) - 'a']++;
            }
            int sLeft = (s.length() + 1) / 2;
            int tLeft = s.length() / 2;
            int[] ansSCnt = new int[26];
            int sLargest = 0;
            int sSmallest = -1;
            for (int i = 0; i < 26; i++) {
                if (sCnt[i] > 0 && sSmallest == -1) {
                    sSmallest = i;
                }
                if (sCnt[i] >= sLeft) {
                    ansSCnt[i] = sLeft;
                    sLargest = i;
                    break;
                } else {
                    ansSCnt[i] = sCnt[i];
                    sLeft -= sCnt[i];
                }
            }
            int[] ansTCnt = new int[26];
            int tSmallest = 0;
            int tLargest = -1;
            for (int i = 25; i >= 0; i--) {
                if (tCnt[i] > 0 && tLargest == -1) {
                    tLargest = i;
                }
                if (tCnt[i] >= tLeft) {
                    ansTCnt[i] = tLeft;
                    tSmallest = i;
                    break;
                } else {
                    ansTCnt[i] = tCnt[i];
                    tLeft -= tCnt[i];
                }
            }
            char[] ans = new char[s.length()];
            int indLeft = 0;
            int indRight = ans.length - 1;
            for (int i = 0; i < ans.length; i++) {
                if (sLargest <= tSmallest) {
                    if (i % 2 == 0) {
                        while (sCnt[sSmallest] == 0) sSmallest++;
                        ans[indLeft] = (char) (sSmallest + 'a');
                        indLeft++;
                        sCnt[sSmallest]--;
                    } else {
                        while (tCnt[tLargest] == 0) tLargest--;
                        ans[indLeft] = (char) (tLargest + 'a');
                        indLeft++;
                        tCnt[tLargest]--;
                    }
                } else {
                    if (i % 2 == 0) {
                        while (sCnt[sLargest] == 0) sLargest--;
                        ans[indRight] = (char) (sLargest + 'a');
                        indRight--;
                        sCnt[sLargest]--;
                    } else {
                        while (tCnt[tSmallest] == 0) tSmallest++;
                        ans[indRight] = (char) (tSmallest + 'a');
                        indRight--;
                        tCnt[tSmallest]--;
                    }
                }
            }
            out.println(ans);
        }

    }

    static class InputReader {
        private BufferedReader reader;
        private StringTokenizer stt;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream));
        }

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

        public String next() {
            while (stt == null || !stt.hasMoreTokens()) {
                stt = new StringTokenizer(nextLine());
            }
            return stt.nextToken();
        }

    }
}

