diff --git a/day16.m b/day16.m
index 50032d6..f514462 100644
--- a/day16.m
+++ b/day16.m
@@ -93,22 +93,22 @@ max_release(Time, Here, Graph, Rates, !Open, Max) :-
     MaxHere = 0),
   Nexts = [Here | set.to_sorted_list(lookup_from(Graph, Here))],
   max_releases(Time - 1, Nexts, Graph, Rates, StartOpen, Outs),
-  get_max([{!.Open, MaxHere} | Outs], !:Open, Max).
+  get_max([o(!.Open, MaxHere) | Outs], o(!:Open, Max)).
 
-:- type out == {open, int}.
+:- type out ---> o(open :: open, max :: int).
 
 :- pred max_releases(int, list(key), graph, rates, open, list(out)).
 :- mode max_releases(in, in, in, in, in, out) is det.
 max_releases(_, [], _, _, _, []).
-max_releases(Time, [Here|Theres], Graph, Rates, Open0, [{Open, Max} | Rest]) :-
+max_releases(Time, [Here|Theres], Graph, Rates, Open0, [o(Open, Max) | Rest]) :-
   max_release(Time, Here, Graph, Rates, Open0, Open, Max) &
   max_releases(Time, Theres, Graph, Rates, Open0, Rest).
 
-:- pred get_max(list(out)::in(non_empty_list), open::out, int::out) is det.
-get_max([{O, M}], O, M).
-get_max([{O, M}, R | Rest], O0, M0) :-
-  get_max([R | Rest], OR, MR),
-  (if M >= MR then O0 = O, M0 = M else O0 = OR, M0 = MR).
+:- pred get_max(list(out)::in(non_empty_list), out::out) is det.
+get_max([O], O).
+get_max([O, R | Rest], O0) :-
+  get_max([R | Rest], OR),
+  (if O^max >= OR^max then O0 = O else O0 = OR).
 
 run(one, Lines, int(Max)) :-
   if lines(Lines, G, R) then max_release(30, "AA", G, R, Max)