import java.util.Scanner;
import java.util.Arrays;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        StringBuilder sb = new StringBuilder(in.next());
        String t = in.next();
        char[] a = t.toCharArray();

        Arrays.sort(a);

        for(int i=a.length-1; i>=0; i--){
            for(int j=0; j<sb.length(); j++){
                if(sb.charAt(j)<a[i]){
                    sb.setCharAt(j, a[i]);
                    break;
                }
            }
        }

        System.out.println(sb.toString());
    }
}