From wikipedia:

https://upload.wikimedia.org/wikipedia/commons/d/d2/San_Fran...

I like it personally. But I much prefer Google's new version of Roboto:

https://camo.githubusercontent.com/3e191ddf621d46efd1fbfa919...

Note that that’s the version from the watch, which has substantially different shapes (most notably is less rounded) and metrics than the version for phones / computers, and is not appropriate for the size of type shown in the Wikipedia diagram.