path(Start, Dest, [[Start,Dest]]) :- connected(Start, Dest).
path(Start, Dest, [[Start, Waypoint]|Path]) :- dif(Dest, Waypoint),
    connected(Start, Waypoint), path(Waypoint, Dest, Path).

alldifferent(_,[]).
alldifferent(X,[L|Ls]) :- dif(X,L), alldifferent(X,Ls).

pathaux(Start, Dest, [Start,Dest],Q) :- connected(Start, Dest), alldifferent(Start,Q).
pathaux(Start, Dest, [Start, Waypoint|Path],Q) :- dif(Dest, Waypoint),
    connected(Start, Waypoint),
    pathaux(Waypoint, Dest, Path, [Start|Q]), alldifferent(Start,Q).

path(X,Y,Z) :- pathaux(X,Y,Z,[]).

connected(ataba,naguib).
connected(naguib,sadat).
connected(sadat,opera).
connected(opera,dokki).
connected(opera,ataba). //Note this one