compress(L,C).
compress([],[]).
compress([a],[a,1]).
compress([b,b],[b,2]).
compress([c,d],[c,1,d,1]).
compress([e,e,e],[e,3]).
compress([f,f,g],[f,2,g,1]).
compress([h,i,i],[h,1,i,2]).
compress([j,k,l],[j,1,k,1,l,1]).

compress([X],[X,1]).
compress([X,Y],[X,2]) :- X=Y.
compress([X,Y],[X,1,Y,1]) :- X\=Y.

