% Adapted from LP/talp_apt/lte.pl
% terminating

%query: goal.
goal :- lte(X,s(s(s(s(0))))), even(X).

lte(0,Y) :- !.
lte(X,s(Y)) :- p(X,P), lte(P,Y).

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

p(0,0).
p(s(X),X).