mysort([], []).
mysort(L1, [X|L3]) :- min_elem(X, L1), delete_first(X, L1, L2), mysort(L2, L3).

min_elem(X, [X|[]]) :- !.
min_elem(N, [X|L1]) :- min_elem(Y, L1), min(X, Y, N), !.

min(X, Y, X) :- X =< Y, !.
min(X, Y, Y) :- X > Y.

delete_first(E, [E|R], R) :- !.
delete_first(E, [X|R1], [X|R2]) :- delete_first(E, R1, R2).