Japanese only
[here](https://cute-0tter.hatenablog.com/entry/2019/01/28/153836#RECON-60pts-Where-is-the-IRC-306-solves)

Original writeup (https://cute-0tter.hatenablog.com/entry/2019/01/28/153836#RECON-60pts-Where-is-the-IRC-306-solves).