cmmdc(X,0,X).
cmmdc(X,Y,Z):- R is X mod Y, cmmdc(Y,R,Z).

cmmmc(X,Y,Z) :- Prod is X*Y, cmmdc(X,Y,C), Z is Prod/C.

sum([],0).
sum([H|T],R):- sum(T,R1),
			  R is R1+H.

separare_par([],[],[]).
separare_par([H|T],[H|E],O):- 0 is H mod 2,!,
							  separare_par(T,E,O).
separare_par([H|T],E,[H|O]):-separare_par(T,E,O).

replace_all(H,Y,[H|T],[Y|R]):- !,replace_all(H,Y,T,R).
replace_all(X,Y,[H|T],[H|R]):- replace_all(X,Y,T,R).
replace_all(_,_,[],[]).

sterge_k(L,P,R):- sterge_k(L,0,P,R).
sterge_k([_|T],N,P,R):- N1 is N+1,
						0 is N1 mod P,!,
						sterge_k(T,N1,P,R).
sterge_k([H|T],N,P,[H|R]):- N1 is N+1,
							sterge_k(T,N1,P,R).
sterge_k([],_,_,[]).

reverse(L,[]):-var(L),!.
reverse([],[]).
reverse([H|T],R):- reverse(T,R1),
				   append(R1,[H],R).