If you think that I am interested in Fibonacci calculators... I mean you are not wrong: I have a Gist I think on doing Fibonaccis by matrix exponentiation which is kind of fun. But in this particular case, no, I don't need to calculate Fibonaccis for any particular reason. It is just a nice project that I can do recursively and then refactor iteratively, and it requires getting some ideas about retrieving environment variables (is Fib[0] 1 or 0?) and command-line arguments.