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.Arrays;
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;
		FastScanner in = new FastScanner(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, FastScanner in, PrintWriter out) {
			char[] s = in.next().toCharArray();
			char[] t = in.next().toCharArray();
			int n = s.length;
			int[] a = frequencies(s, (n + 1) / 2, true);
			int[] b = frequencies(t, n / 2, false);
			char[] ans = new char[n];
			int l = 0;
			int r = n - 1;
			int la = 0;
			int ra = 25;
			int lb = 0;
			int rb = 25;
			for (int step = 0; step < n; step++) {
				while (la <= ra && a[la] == 0) {
					++la;
				}
				while (la <= ra && a[ra] == 0) {
					--ra;
				}
				while (lb <= rb && b[lb] == 0) {
					++lb;
				}
				while (lb <= rb && b[rb] == 0) {
					--rb;
				}
				if (step % 2 == 0) {
					if (rb > la) {
						ans[l++] = (char) (la + 'a');
						--a[la];
					} else {
						ans[r--] = (char) (ra + 'a');
						--a[ra];
					}
				} else {
					if (la < rb) {
						ans[l++] = (char) (rb + 'a');
						--b[rb];
					} else {
						ans[r--] = (char) (lb + 'a');
						--b[lb];
					}
				}
			}
			out.println(new String(ans));
		}

		private int[] frequencies(char[] s, int am, boolean fromStart) {
			Arrays.sort(s);
			int[] f = new int[26];
			for (int i = 0; i < am; i++) {
				char c;
				if (fromStart) {
					c = s[i];
				} else {
					c = s[s.length - i - 1];
				}
				++f[c - 'a'];
			}
			return f;
		}

	}

	static class FastScanner {
		private BufferedReader in;
		private StringTokenizer st;

		public FastScanner(InputStream stream) {
			in = new BufferedReader(new InputStreamReader(stream));
		}

		public String next() {
			while (st == null || !st.hasMoreTokens()) {
				try {
					String rl = in.readLine();
					if (rl == null) {
						return null;
					}
					st = new StringTokenizer(rl);
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			return st.nextToken();
		}

	}
}

