> Write a predicate `f/2` (i.e. a predicate with name `f` and 2 arguments) which states that its second argument is the factorial of its first argument.
To do integer operations, add `:- use_module(library(clpfd)).` at the beginning of your code base. Some operations you might need are (with dummy variables): `A #> B`, `A #= B * C`, `A #= B - C`.
