> For the complete documentation index, see [llms.txt](https://www.oulan.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.oulan.com/2019/10/18.md).

# 18

<figure><img src="https://385430918-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M8iFCzaIpXf8zXqpE6I%2Fuploads%2F6BGcW0BrAZgI07QSVyRl%2Fimage.png?alt=media&amp;token=10d42e15-d1e9-4daf-8683-3bfa24e33b93" alt=""><figcaption></figcaption></figure>