r(a(l), a(a(a(l)))).
r(a(X), a(a(a(Y)))) :- r(X,Y).

r(a(b(a(a(a(l))))), a(b(l))).
r(a(b(a(a(a(X))))), a(b(Y))) :- r(X,Y).

r(a(b(l)), b(l)).
r(a(b(X)), b(Y)) :- r(X,Y).

pcpHatLoesung :- r(X,X).


% Abgeleiteter Fakt:
% r(a(b(a(a(a(a(a(a(b(l))))))))), a(b(a(a(a(a(a(a(b(l))))))))))