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

bccdb
 z
 dfdeed
 aab
 y
 abac


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

public class TestClass {

	static PrintWriter out = new PrintWriter(System.out);
	public static void main(String[] args) throws Exception{
		
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String x = in.readLine();
		String y = in.readLine();
		int n = x.length();
		char a[] = x.toCharArray();
		char b[] = y.toCharArray();
		Arrays.sort(a);
		Arrays.sort(b);
		int i1=0,j1=n/2,i2=n/2+1,j2=n-1;
		char ans[] = new char[n];
		int p=0,q=n-1,f=0,k=0;
		while(k<n)
		{
			if(f==0)
			{
				if(a[i1]>b[j2])
				{
					ans[q] = a[j1];
					j1--;
					q--;
				}
				else
				{
					ans[p] = a[i1];
					i1++;
					p++;
				}
				f=1;
			}
			else
			{
				if(a[i1]>b[j2])
				{
					ans[q] = b[i2];
					i2++;
					q--;
				}
				else
				{
					ans[p] = b[j2];
					j2--;
					p++;
				}
				f=0;
			}
			k++;
		}
		for(int i=0;i<n;i++)
		{
			out.print(ans[i]);
		}
		out.close();
	}
	
}	
