# 1881. Maximum Value after Insertion

https://leetcode.com/problems/maximum-value-after-insertion

## Description

You are given a very large integer `n`, represented as a string,​​​​​​ and an integer digit `x`. The digits in `n` and the digit `x` are in the **inclusive** range `[1, 9]`, and `n` may represent a **negative** number.

You want to **maximize** `n`**'s numerical value** by inserting `x` anywhere in the decimal representation of `n`​​​​​​. You **cannot** insert `x` to the left of the negative sign.

* For example, if `n = 73` and `x = 6`, it would be best to insert it between `7` and `3`, making `n = 763`.
* If `n = -55` and `x = 2`, it would be best to insert it before the first `5`, making `n = -255`.

Return _a string representing the **maximum** value of_ `n`_​​​​​​ after the insertion_.

**Example 1:**

```
**Input:** n = "99", x = 9
**Output:** "999"
**Explanation:** The result is the same regardless of where you insert 9.
```

**Example 2:**

```
**Input:** n = "-13", x = 2
**Output:** "-123"
**Explanation:** You can make n one of {-213, -123, -132}, and the largest of those three is -123.
```

**Constraints:**

* `1 <= n.length <= 105`
* `1 <= x <= 9`
* The digits in `n`​​​ are in the range `[1, 9]`.
* `n` is a valid representation of an integer.
* In the case of a negative `n`,​​​​​​ it will begin with `'-'`.

## ac

```java
```
