:- op(500, xfx  , parent_of).

lali    parent_of  soso.
lali    parent_of  ana.
gia    parent_of  ana.
gia    parent_of  soso.
ana   parent_of  miriam.
ana   parent_of  rezo.

ancestor_of(Anc, Child) :-
	parent_of(Anc, Child).
ancestor_of(Anc, Child) :-
	parent_of(Anc, X),
	ancestor_of(X, Child).