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

bccdb
 z
 dfdeed
 aab
 y
 abac


/**
 * DA-IICT
 * Author : Savaliya Sagar
 */
import java.io.*;
import java.math.*;
import java.util.*;

public class C794 {
	InputStream is;
	PrintWriter out;
	String INPUT = "";

	void solve() {
		int a[] = new int[26];
		int b[] = new int[26];
		String s = ns();
		int n = s.length();
		for (int i = 0; i < n; i++)
			a[s.charAt(i) - 'a']++;
		s = ns();
		for (int i = 0; i < n; i++)
			b[s.charAt(i) - 'a']++;
		int r1 = n / 2;
		int r2 = (int) Math.ceil(n / 2.0);
		for (int i = 25; i >= 0; i--) {
			int min = Math.min(r1, a[i]);
			a[i] -= min;
			r1 -= min;
		}
		for (int i = 0; i <= 25; i++) {
			int min = Math.min(r2, b[i]);
			b[i] -= min;
			r2 -= min;
		}
		char c[] = new char[n];
		int start = 0;
		int end = n - 1;
		int maxa = max(a, 25);
		int maxb = max(b, 25);
		int mina = min(a, 0);
		int minb = min(b, 0);
		int flag = 0;
		for (int i = 0; i < n ; i++) {
			if (mina >= maxb) {
				if (flag == 0) {
					c[end--] = (char) (maxa + 'a');
					a[maxa]--;
					maxa = max(a, maxa);
				}else{
					c[end--] = (char)(minb+'a');
					b[minb]--;
					minb = min(b,minb);
				}
			} else {
				if(flag==0){
					c[start++]=(char)(mina+'a');
					a[mina]--;
					mina = min(a,mina);
				}else{
					c[start++] = (char)(maxb+'a');
					b[maxb]--;
					maxb = max(b,maxb);
				}
			}
			flag^=1;
		}
		for (char k : c)
			out.print(k);

	}

	int min(int a[], int min) {
		for (int i = min; i < 26; i++) {
			if (a[i] != 0)
				return i;
		}
		return -1;
	}

	int max(int a[], int max) {
		for (int i = max; i >= 0; i--) {
			if (a[i] != 0)
				return i;
		}
		return -1;
	}

	void run() throws Exception {
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);

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

	public static void main(String[] args) throws Exception {
		new Thread(null, new Runnable() {
			public void run() {
				try {
					new C794().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 void tr(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}
}
