> 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/2019/01/20.md).

# 20

![](https://385430918-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M8iFCzaIpXf8zXqpE6I%2F-MTU15mxqF5uGvVNUHDU%2F-MTU1ALOZKVmGuLOGehA%2Fimage.png?alt=media\&token=7991180e-2e35-4387-bd48-ed35d6d40a3c)