lm-kasuga

The variable `len` is `int`, but `%u` is used. This may cause UB(but the compiler doesn't say any errors or warnings. ref. [https://stackoverflow.com/questions/11303784/why-doesnt-gcc-wformat-warn-about-printf-d-on-an-unsigned-int](https://stackoverflow.com/questions/11303784/why-doesnt-gcc-wformat-warn-about-printf-d-on-an-unsigned-int)) We should use `%d` instead, or change...