CF915C.Permute Digits

You are given two positive integer numbers a and b. Permute (change order) of the digits of a to construct maximal number not exceeding b. No number in input and/or output can start with the digit 0.

It is allowed to leave a as it is.

给你两个正整数 $a$ 和 $b$。请重排（即改变顺序）$a$ 的各位数字，构造出不超过 $b$ 的最大可能的数。输入和/或输出中的任何数字均不能以数字 $0$ 开头。

允许保持 $a$ 不变。

The first line contains integer a (1 ≤ a ≤ 1018). The second line contains integer b (1 ≤ b ≤ 1018). Numbers don't have leading zeroes. It is guaranteed that answer exists.

第一行包含整数 $a$（$1 \leq a \leq 10^{18}$）。
第二行包含整数 $b$（$1 \leq b \leq 10^{18}$）。
数字不含前导零。
保证答案存在。

Print the maximum possible number that is a permutation of digits of a and is not greater than b. The answer can't have any leading zeroes. It is guaranteed that the answer exists.

The number in the output should have exactly the same length as number a. It should be a permutation of digits of a.

输出一个由数字 a 的各位数字重新排列得到的最大可能的数，且该数不大于 b。答案不能有前导零。保证答案存在。

输出的数字应与数字 a 的长度完全相同，且必须是 a 的各位数字的一个排列。