CF169B.Replacing Digits

You are given an integer a that consists of n digits. You are also given a sequence of digits s of length m. The digit in position j (1 ≤ j ≤ m) of sequence s means that you can choose an arbitrary position i (1 ≤ i ≤ n) in a and replace the digit in the chosen position i with s__j. Each element in the sequence s can participate in no more than one replacing operation.

Your task is to perform such sequence of replacements, that the given number a gets maximum value. You are allowed to use not all elements from s.

给你一个由 $n$ 位数字组成的整数 $a$。同时给你一个长度为 $m$ 的数字序列 $s$。序列 $s$ 中第 $j$ 个位置（$1 \le j \le m$）上的数字表示：你可以任选 $a$ 中的一个位置 $i$（$1 \le i \le n$），并将该位置上的数字替换为 $s_j$。序列 $s$ 中的每个元素最多只能参与一次替换操作。

你的任务是执行一系列替换操作，使得给定的数字 $a$ 达到最大值。你不必使用 $s$ 中的所有元素。

The first line contains positive integer a. Its length n is positive and doesn't exceed 105. The second line contains sequence of digits s. Its length m is positive and doesn't exceed 105. The digits in the sequence s are written consecutively without any separators.

The given number a doesn't contain leading zeroes.

第一行包含一个正整数 $a$。其长度 $n$ 为正，且不超过 $10^5$。第二行包含一个数字序列 $s$。其长度 $m$ 为正，且不超过 $10^5$。序列 $s$ 中的数字连续书写，中间不加任何分隔符。

给定的数字 $a$ 不含前导零。

Print the maximum value that can be obtained from a after a series of replacements. You are allowed to use not all elements from s. The printed number shouldn't contain any leading zeroes.

输出经过一系列替换后，字符串 a 能得到的最大值。允许不使用 s 中的全部元素。输出的数字不能包含前导零。