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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.*;
import java.util.*;
import java.math.*;

public final class round_414_c
{
    static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	static FastScanner sc=new FastScanner(br);
    static PrintWriter out=new PrintWriter(System.out);
	static Random rnd=new Random();
	
	static int min(int[] a)
	{
		for(int i=0;i<26;i++)
		{
			if(a[i]>0)
			{
				return i;
			}
		}
		
		return -1;
	}
	
	static int max(int[] a)
	{
		for(int i=25;i>=0;i--)
		{
			if(a[i]>0)
			{
				return i;
			}
		}
		
		return -1;
	}
	
    public static void main(String args[]) throws Exception
    {
		char[] a=sc.next().toCharArray(),b=sc.next().toCharArray();int n=a.length;
		
		Arrays.sort(a);Arrays.sort(b);
		
		for(int i=0,j=n-1;i<j;i++,j--)
		{
			char temp=b[i];b[i]=b[j];b[j]=temp;
		}
		
		char[] res=new char[n];
		
		//out.println(Arrays.toString(a)+" "+Arrays.toString(b));
		
		int[][] cnt=new int[2][26];
		
		for(int i=1;i<=(n/2)+(n%2);i++)
		{
			cnt[0][a[i-1]-'a']++;
		}
		
		for(int i=1;i<=n/2;i++)
		{
			cnt[1][b[i-1]-'a']++;
		}
		
		//out.println(Arrays.toString(cnt[0])+" "+Arrays.toString(cnt[1]));
		
		int min=min(cnt[0]),max=max(cnt[1]);
		
		ArrayDeque<Integer> ad=new ArrayDeque<>();
		
		for(int i=0;i<n;i++)
		{
			ad.add(i);
		}
		
		for(int i=0;i<n;i++)
		{
			if(i%2==0)
			{
				if(min<max)
				{
					int idx=ad.removeFirst();res[idx]=(char)(min+'a');
					
					cnt[0][min]--;
				}
				
				else
				{
					int curr_max=max(cnt[0]);
					
					int idx=ad.removeLast();
					
					res[idx]=(char)(curr_max+'a');
					
					cnt[0][curr_max]--;
				}
				
				min=min(cnt[0]);
			}
			
			else
			{
				if(max>min)
				{
					int idx=ad.removeFirst();res[idx]=(char)(max+'a');
					
					cnt[1][max]--;
				}
				
				else
				{
					int curr_min=min(cnt[1]);
					
					int idx=ad.removeLast();
					
					res[idx]=(char)(curr_min+'a');
					
					cnt[1][curr_min]--;
				}
				
				max=max(cnt[1]);
			}
		}
		
		out.println(new String(res));out.close();
    }
}
class FastScanner
{
    BufferedReader in;
    StringTokenizer st;

    public FastScanner(BufferedReader in) {
        this.in = in;
    }
	
    public String nextToken() throws Exception {
        while (st == null || !st.hasMoreTokens()) {
            st = new StringTokenizer(in.readLine());
        }
        return st.nextToken();
    }
	
	public String next() throws Exception {
		return nextToken().toString();
	}
	
    public int nextInt() throws Exception {
        return Integer.parseInt(nextToken());
    }

    public long nextLong() throws Exception {
        return Long.parseLong(nextToken());
    }

    public double nextDouble() throws Exception {
        return Double.parseDouble(nextToken());
    }
}