import java.io.*;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.*;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Set;
import java.util.StringTokenizer;

public class squad_nk implements Runnable {

	private String nextToken() {
		if (st1 == null || !st1.hasMoreTokens()) {
			try {
				String p = in.readLine();
				if (p == null) {
					return null;
				}
				st1 = new StringTokenizer(p);
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return st1.nextToken();
	}

	private int nextInt() {
		return new Integer(nextToken());
	}

	private long nextLong() {
		return new Long(nextToken());
	}

	private StringTokenizer st1;
	private BufferedReader in;
	private PrintWriter out;

	@Override
	public void run() {
		try {
			in = new BufferedReader(new FileReader("squad.in"));
			out = new PrintWriter(new FileWriter("squad.out"));
			String n = nextToken();
			String m = nextToken();
			String s = new String();
			for (int i = 0; i<n.length(); i++){
				if (n.charAt(i) > m.charAt(i))
					s += n.charAt(i);
				else
					s += m.charAt(i);
			}
			out.print(s);
			in.close();
			out.close();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

	public static void main(String[] args) {
		new Thread(new squad_nk()).start();
	}

}