One way to be sure what the code is doing is writing unit tests. Just dumb black boxing is fine: `assert f(0) == 0`. When it returns "Pancake", change to `asse

One way to be sure what the code is doing is writing unit tests. Just dumb black boxing is fine: `assert f(0) == 0`. When it returns "Pancake", change to `assert f(0) == "Pancake"` ...repeat until you understand :)