reachable(Station1, Limit, Result) :-
     reachable(Station1, [Station1], 0, Limit, Result).

reachable(Station1, Visited, TimeSpent, Limit, Result) :-
            (
            overground(Station1, Station2, Time);
            overground(Station2, Station1, Time)
            ),
            \+member(Station2,Visited),
            NewTimeSpent is TimeSpent + Time,
            (
            NewTimeSpent =< Limit,
            Result = Station2
            ;
            reachable(Station2, [Station2|Visited], NewTimeSpent, Limit, Result)
            ).