Reachability without recursion

Which stations can you reach from Taipei Main Station?

We could write one rule per number of stops:

reach(X, Y) :- line(X, Y).                            # 1 stop
reach(X, Y) :- line(X, Z), line(Z, Y).                # 2 stops
reach(X, Y) :- line(X, Z), line(Z, W), line(W, Y).    # 3 stops

Three rules are enough for our metro, but more stops need more rules!