A challenge to find some files which have invalid md5 values.
Not so hard but somewhat guessing.

[writeup](https://ptr-yudai.hatenablog.com/entry/2019/03/09/215844#Code-488-navigation-records)

Original writeup (https://ptr-yudai.hatenablog.com/entry/2019/03/09/215844#Code-488-navigation-records).