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

public class C {

	static int n;
	static char[] a, b;
	
	public static void main(String[] args) throws Exception{

		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		a = sc.next().toCharArray(); b = sc.next().toCharArray();
		Arrays.sort(a); Arrays.sort(b);
		n = a.length;
		char[] ans = new char[n];
		int i = 0, j = n-1, idx = 0, l = 0, r = n-1;
		while(idx < n)
		{
			if(idx % 2 == 0)
			{
				int bs = bsUpper((n-1)/2+1, j, a[i]);
				if(bs == -1) {ans[r] = a[i]; r--;}
				else {ans[l] = a[i]; l++;}
				i++;
			}
			else
			{
				int bs = bsLower(i, (n-1)/2, b[j]);
				if(bs == -1){ans[r] = b[j]; r--;}
				else {ans[l] = b[j]; l++;}
				j--;
			}
			idx++;
		}
		for(char c : ans) out.print(c);
		out.println();
		out.flush();
		out.close();
	}
	
	static int bsUpper(int lo, int hi, char t)
	{
		int ans = -1;
		while(lo <= hi)
		{
			int mid = (lo + hi) / 2;
			if(b[mid] >= t) hi = (ans = mid) - 1;
			else lo = mid + 1;
		}
		return ans;
	}
	
	static int bsLower(int lo, int hi, char t)
	{
		int ans = -1;
		while(lo <= hi)
		{
			int mid = (lo + hi) / 2;
			if(a[mid] <= t) lo = (ans = mid) + 1;
			else hi = mid - 1;
		}
		return ans;
	}

	static class Scanner 
	{
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream System){br = new BufferedReader(new InputStreamReader(System));}
		public String next() throws IOException 
		{
			while (st == null || !st.hasMoreTokens()) 
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}
		public String nextLine()throws IOException{return br.readLine();}
		public int nextInt() throws IOException {return Integer.parseInt(next());}
		public double nextDouble() throws IOException {return Double.parseDouble(next());}
		public char nextChar()throws IOException{return next().charAt(0);}
		public Long nextLong()throws IOException{return Long.parseLong(next());}
		public boolean ready() throws IOException{return br.ready();}
		public void waitForInput(){for(long i = 0; i < 3e9; i++);}
	}
}