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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.*;
import java.util.*;
public class Main {

	public static void main(String[] args) {
		FastScanner sc=new FastScanner();
		PrintWriter pw=new PrintWriter(System.out);
		while(sc.hasNext()){
			String s1=sc.next();
			String s2=sc.next();
			char[] res=new char[s1.length()];
			Character[]a=new Character[s1.length()];
			Character[]b=new Character[s1.length()];
			for(int i=0;i<s1.length();i++){
				a[i]=s1.charAt(i);
				b[i]=s2.charAt(i);
			}
			Arrays.sort(a);
			Arrays.sort(b,new Comparator<Character>(){
				public int compare(Character a, Character b) {
					if(a.charValue()<b.charValue())return 1;
					if(a.charValue()>b.charValue())return -1;
					return 0;
				}
			});
			int count=0;
			int start=0;
			int as=0;
			int bs=0;
			int ad=(s1.length()+1)/2-1;
			int bd=s1.length()/2-1;
			int end=s1.length()-1;
			while(count<s1.length()){
				count++;
				if(count%2!=0){
					if(a[as]>=b[bs]){
						res[end--]=a[ad--];
					}else{
						res[start++]=a[as++];
					}
				}else{
					if(b[bs]<=a[as]){
						res[end--]=b[bd--];
					}else{
						res[start++]=b[bs++];
					}
				}
				}
			for(int i=0;i<s1.length();i++) pw.print(res[i]);
			pw.flush();
		}

	}

}
class FastScanner {
	BufferedReader br;
	StringTokenizer st;

	public FastScanner() {
		try {
			br = new BufferedReader(new InputStreamReader(System.in));
			st = new StringTokenizer("");
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public boolean hasNext() {
		while (!st.hasMoreTokens()) {
			String line = nextLine();
			if (line == null) {
				return false;
			}
			st = new StringTokenizer(line);
		}
		return true;
	}

	public String next() {
		if (st.hasMoreTokens())
			return st.nextToken();
		try {
			st = new StringTokenizer(br.readLine());
		} catch (Exception e) {
			e.printStackTrace();
		}
		return st.nextToken();
	}

	public int nextInt() {
		return Integer.parseInt(next());
	}

	public long nextLong() {
		return Long.parseLong(next());
	}

	public double nextDouble() {
		return Double.parseDouble(next());
	}

	public String nextLine() {
		String line = "";
		try {
			line = br.readLine();
		} catch (Exception e) {
			e.printStackTrace();
		}
		return line;
	}
}