parent(nikos,kostas).
parent(kostas,manolis).
parent(manolis,maria).
parent(manolis,eleni).
parent(eleni,giorgos).

ancestor1(X,Y):-parent(X,Y).
ancestor1(X,Y):-parent(X,Z),ancestor1(Z,Y).

ancestor2(X,Y):-parent(X,Y).
ancestor2(X,Y):-parent(Z,Y),ancestor2(X,Z).

ancestor3(X,Y):-parent(X,Z),ancestor3(Z,Y).
ancestor3(X,Y):-parent(X,Y).

ancestor4(X,Y):-parent(X,Y).
ancestor4(X,Y):-ancestor4(Z,Y),parent(X,Z).

ancestor5(X,Y):-ancestor5(Z,Y),parent(X,Z).
ancestor5(X,Y):-parent(X,Y).