:- set_prolog_flag(verbose,silent).
:- prompt(_, '').
:- use_module(library(readutil)).

main:-
	process,
	halt.

woman(lisa).
woman(maggie).
parents(lisa, homer, marge).
parents(maggie, homer, marge).
sister(X, Y):-
  woman(Y),
  parents(X, P, M),
  parents(Y, P, M),
  X \= Y.

process:-
	sister(lisa, X),
	write(X),
	true.

:- main.