I made a web service where you can easily play with the trendy Lean! It only verifies proofs, so you can't do anything bad to the server, right?
Beginner Hint
- The flag is stored in
/flag-<md5hash>.txt. Your goal is to read it. - Lean is a theorem prover, but it is also a functional programming language. In particular, Lean 4 has stronger support for general-purpose programming.
- Try researching how to execute OS commands in Lean.