Natural number in SWI-prolog & recursive procedure

Question

I have the next procedure for natural number is SWI-prolog:

natural_number(0).
natural_number(s(X)) :- natural_number(X).

Now I want to do

Answer 1

natural_number(s(0), 0).
natural_number(s(s(X)), N) :- natural_number(s(X), S), N is S + 1.