directTrain(saarbruecken,dudweiler). 
   directTrain(forbach,saarbruecken). 
   directTrain(freyming,forbach). 
   directTrain(stAvold,freyming). 
   directTrain(fahlquemont,stAvold). 
   directTrain(metz,fahlquemont). 
   directTrain(nancy,metz).
   
   travelFromTo(A, B):-
   directTrain(A,B).
   travelFromTo(A, C):-
   directTrain(A, B),
   travelFromTo(B, C).