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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.util.*;

public class contest19 {
	static final int e9 = 1000000000;
	static Scanner scn = new Scanner(System.in);	
	
	public static void main(String[] args) {
		String one = scn.next();
		String two = scn.next();
		int n = one.length();
		char[] small = one.toCharArray();
		Arrays.sort(small);
		char[] large = two.toCharArray();
		Arrays.sort(large);
		
		char[] ans = new char[n];
		int i=0,j=n-1; // for small and large starting
		int m1,m2; // mid of small and large array
		if(n%2==0) {
			m1=n/2-1;
			m2=n/2;
		}
		else {
			m1=n/2;
			m2=n/2+1;
		}
		int s=0,e=n-1; // for ans array pointers
		
		for(int l=0;l<n;l++) {
			if(l%2==0) {
				if(small[i]<large[j])
					ans[s++]=small[i++];
				else
					ans[e--]=small[m1--];
			}
			else {
				if(large[j]>small[i])
					ans[s++]=large[j--];
				else
					ans[e--]=large[m2++];
			}
		}
//		for(char ch:ans)
//			System.out.print(ch);
		String str = new String(ans);
		System.out.println(str);
	}
}
				 	  	  				    				  	  	 	