> 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/2017/03/18.md).

# 18

![](https://385430918-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M8iFCzaIpXf8zXqpE6I%2F-MTXzkxEZaGsQjzyBZCC%2F-MTY-0X8xv5kl_aL2-11%2Fimage.png?alt=media\&token=7c39b06e-62ba-4e5f-bea0-891fabfc14f5)