Solution by Ben Davies

# Using the Solutions

- Install
  [Idris](https://github.com/idris-lang/Idris-dev/wiki/Installation-Instructions)
  and ensure its executable is in your path.
- Run `$ make -j2`. The executables for the challenges will be output to
  `./ch-1` and `./ch-2`.
- Run `$ make clean` to remove compiled objects or `$ make distclean` to
  remove the executables as well, if you wish.