*Inspired by [There, I fixed it (with rope)](https://codegolf.stackexchange.com/questions/157600/there-i-fixed-it-with-rope), [There, I fixed it (with Tape)](https://codegolf.stackexchange.com/questions/157240/there-i-fixed-it-with-tape), [There, I broke it (with scissors)](https://codegolf.stackexchange.com/questions/157612/there-i-broke-it-with-scissors)*

Given a string with characters from `a-z` or `A-Z` (whichever you prefer), turn missing letters into numbers and make them explode.

---

Example
=======

Input: `abcafabc`

Output: `a12344321c`

***Why?***

1) Find the missing letters (only going forward in the alphabet): `abca(bcde)fabc`

2) Replace them with the number of missing letters: `abca4fabc`

3) Replace the number with

* Itself twice if it's even
* Itself + 1 if it's odd

In this case: `abca44fabc`

4) Explode those numbers outwards replacing any letters: `a12344321c`

---

Challenge Rules
===============

1. Explosions can't exceed the boundaries of the string

	* `ae -> 343` (3 letters are missing but since 3 is odd, it's been replaced by 4)
2. Numbers can be greater than 9

	* `az -> 23242423` (24 letters are missing and since 24 is even, it's repeated twice)
3. You can have multiple explosions

	* `abcefghijmnop -> ab121fghi1221nop`
4. Multiple explosions can overlap, take the sum of the number when they do

	* `abceghij -> abc(2)e(2)ghij -> ab12(1+1)21hij -> ab12221hij`
5. It's possible that no explosions occur, in that case simply return the string
6. No explosions between `ab`, `aa`, `aaa`, etc.
7. You are allowed to take the input in any reasonable format. Can be a single string, string-array/list, character-array/list, etc. Output has the same flexibility.
8. You are allowed to use lowercase and/or uppercase any way you'd like. This applies both to the input, output.

General Rules
=============

* This is [code-golf](/questions/tagged/code-golf "show questions tagged 'code-golf'"), so the shortest answer in bytes wins.  

Don't let code-golf languages discourage you from posting answers with non-golfing languages.
* [Standard rules apply](https://codegolf.meta.stackexchange.com/questions/2419/default-for-code-golf-program-function-or-snippet/2422#2422).
* [Default Loopholes](https://codegolf.meta.stackexchange.com/questions/1061/loopholes-that-are-forbidden-by-default) are forbidden.
* If possible, please add a link to a test for your code, preferably [Tio](https://tio.run/#).
* Also, please add an explanation if necessary.

---

Test cases:
===========

```
Input  : 'abcdefgklmnopqrstuvwxyz'
Output : 'abcd1234321nopqrstuvwxyz'

Input  : 'abdefgjkl'
Output : 'a121ef1221kl'

Input  : 'xyzaz'
Output : '20212223242423'

Input  : 'abceghij'
Output : 'ab12221hij'

Input  : 'zrabc'
Output : 'zrabc'

```