// Arup Guha
// 2/10/2024
// Solution to Kattis Problem: Class Field Trip
// https://open.kattis.com/problems/classfieldtrip

import java.util.*;

public class classfieldtrip {

	public static void main(String[] args) {
	
		// Read both lists.
		Scanner stdin = new Scanner(System.in);
		String first = stdin.next();
		String second = stdin.next();
		
		// Concatenate.
		String all = first + second;
		
		// Convert to array.
		char[] arr = all.toCharArray();
		
		// Sort.
		Arrays.sort(arr);
		
		// This works!
		System.out.println(new String(arr));
	}
}
		