> 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/2017/01/16.md).

# 20

![](https://385430918-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M8iFCzaIpXf8zXqpE6I%2F-MSkK518ZZbmpKU7n_8o%2F-MSkKBfMTD6TVJcR-qfM%2Fimage.png?alt=media\&token=b3f993fe-4c5a-4d5e-8f69-2c2220624254)