Just a simple calculator application. Nothing suspicious to see here :)
There is a docker container, and scripts to start the container, for your convenience. However, I recommend just playing around with the ELF files in the respective challenge directory.
The challenges are hosted at server.cerne.xyz:1337 and server.cerne.xyz:1338 for a limited time. Connect to the servers like so:
nc server.cerne.xyz 1337