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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.util.Arrays;
import java.util.Collections;
import java.util.InputMismatchException;
import java.util.PriorityQueue;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;

public class C_414 {

	InputStream is;
	PrintWriter out;
	int n;
	long a[];

	void solve() {
		String s1 = ns();
		String s2 = ns();
		PriorityQueue<Character> q1 = new PriorityQueue<>();
		PriorityQueue<Character> q2 = new PriorityQueue<>(Collections.reverseOrder());
		for (int i = 0; i < s1.length(); i++) {
			q1.add(s1.charAt(i));
			q2.add(s2.charAt(i));
		}
		char c[] = new char[s1.length()];
		int last = s1.length() - 1;
		int first = 0;
		for (int i = 0; i < s1.length(); i++) {
			// out.println(first + " xx> " + last);
			if (i % 2 == 0) {
				// out.println(q1.peek() + " " + q2.peek());
				if (q1.peek() - 'a' > q2.peek() - 'a') {
					c[last] = q1.poll();
					last--;
					// out.println("here");
				} else {
					c[first] = q1.poll();
					first++;
				}
			} else {
				if (q2.peek() < q1.peek()) {
					c[last] = q2.poll();
					last--;
				} else {
					c[first] = q2.poll();
					first++;
				}
			}
			// out.println(first + " --> " + last);
		}
		for (int i = 0; i < c.length; i++) {
			out.print(c[i]);
		}
	}

	void run() throws Exception {
		String INPUT = "C:\\Users\\DHAVAL\\Desktop\\input.txt";
		is = oj ? System.in : new FileInputStream(INPUT);
		out = new PrintWriter(System.out);

		long s = System.currentTimeMillis();
		solve();
		out.flush();
		tr(System.currentTimeMillis() - s + "ms");
	}

	public static void main(String[] args) throws Exception {
		new Thread(null, new Runnable() {
			public void run() {
				try {
					new C_414().run();
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		}, "1", 1 << 26).start();
	}

	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;

	private int readByte() {
		if (lenbuf == -1)
			throw new InputMismatchException();
		if (ptrbuf >= lenbuf) {
			ptrbuf = 0;
			try {
				lenbuf = is.read(inbuf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (lenbuf <= 0)
				return -1;
		}
		return inbuf[ptrbuf++];
	}

	private boolean isSpaceChar(int c) {
		return !(c >= 33 && c <= 126);
	}

	private int skip() {
		int b;
		while ((b = readByte()) != -1 && isSpaceChar(b))
			;
		return b;
	}

	private double nd() {
		return Double.parseDouble(ns());
	}

	private char nc() {
		return (char) skip();
	}

	private String ns() {
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != '
									// ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	private char[] ns(int n) {
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while (p < n && !(isSpaceChar(b))) {
			buf[p++] = (char) b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}

	private char[][] nm(int n, int m) {
		char[][] map = new char[n][];
		for (int i = 0; i < n; i++)
			map[i] = ns(m);
		return map;
	}

	private int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = ni();
		return a;
	}

	private int ni() {
		int num = 0, b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private long nl() {
		long num = 0;
		int b;
		boolean minus = false;
		while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
			;
		if (b == '-') {
			minus = true;
			b = readByte();
		}

		while (true) {
			if (b >= '0' && b <= '9') {
				num = num * 10 + (b - '0');
			} else {
				return minus ? -num : num;
			}
			b = readByte();
		}
	}

	private boolean oj = System.getProperty("ONLINE_JUDGE") != null;

	private void tr(Object... o) {
		if (!oj)
			System.out.println(Arrays.deepToString(o));
	}
}
