firstPlateau(L,P,S).
firstPlateau([a],[a],[]).
firstPlateau([b,b],[b,b],[]).
firstPlateau([c,d],[c],[d]).
firstPlateau([e,f,g],[e],[f,g]).
firstPlateau([h,i,i],[h],[i,i]).
firstPlateau([j,j,k],[j,j],[k]).
firstPlateau([m,m,m],[m,m,m],[]).

firstPlateau([X],[X],[]).
firstPlateau([X,Y],[X,Y],[]) :- X=Y.
firstPlateau([X,Y|T],[X],[Y|T]) :- Y\=X.

