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 `'-'`.