p.
q.
r.
w :- p,r.
v :- w,q,s.
s :- w.


Parent(pam,bob).
parent(tom,bob).
parent(tom,liz).
parent(bob,ann).
parent(bob,pat).
parent(joe,jim).
parent(pat,jim).
male(tom).
male(bob).
male(joe).
male(jim).
female(pam).
female(liz).
female(ann).
female(pat).
child(X,Y) :- parent(Y,X).
mother(X,Y) :- parent(X,Y), female(X).
father(X,Y) :- parent(X,Y), male(X).
grandparent(X,Y) :- parent(X,Z), parent(Z,Y).