append([],L2,L2).
append([H|T],L2,[H|L3]):- append(T,L2,L3).

partition(E,[],[],[]).
partition(E,[H|T],[H|T1],L2):-
	H < E,
	partition(E,T,T1,L2).
partition(E,[H|T],L1,[H|T2]):-
	H @>=E,
	partition(E,T,L1,T2).
	
isort([],[]).
isort([H|T],F):-
	isort(T,L),
	partition(H,L,L1,L2),
	append(L1,[H|L2],F).