Restore +1/-1

[Merge branch 'ptal' of https://github.com/mattn/sushiyuki-for-engineers ... · 5b45168 · awayuki/sushiyuki-for-engineers](https://github.com/awayuki/sushiyuki-for-engineers/commit/5b45168bce6ca6efa7bf15bfd1447266125fb9fa) の時に消えてしまっていたようです