diff --git a/day7.m b/day7.m
index 9aff4a0..ab36eb8 100644
--- a/day7.m
+++ b/day7.m
@@ -10,42 +10,27 @@
 :- import_module string.
 :- import_module list.
 
-
-:- type words == list(string).
-
-:- type file ---> file(name :: string, size :: int).
-:- type files == list(file).
-
-:- type dir --->
-    dir(name :: string,
-        immed :: int, total :: int,
-        files :: files, dirs :: dirs).
+:- type dir ---> dir(size :: int, dirs :: dirs).
+:- func size(dir) = int.
 :- type dirs == list(dir).
-:- func total(dir) = int.
-
-:- pred line(words::out, lines::in, lines::out) is semidet.
-line(words(Line)) --> [Line].
 
 :- pred dir(dir::out, lines::in, lines::out) is nondet.
-dir(dir(Name, Immed, Total, Files, Dirs)) -->
-  cd_down(Name),
-  ["$ ls"], files(Files),
-  {Immed = foldl(func(File, Acc) = size(File) + Acc, Files, 0)},
+dir(dir(Size, Dirs)) -->
+  [Cd], {append("$ cd ", _, Cd)},
+  ["$ ls"],
+  files(Files),
   dirs(Dirs),
-  {Total = foldl(func(Dir, Acc) = total(Dir) + Acc, Dirs, Immed)},
+  {Size = Files + sum(map(size, Dirs))},
   (["$ cd .."] ; []).
 
-:- pred cd_down(string::out, lines::in, lines::out) is semidet.
-cd_down(D) --> line(["$", "cd", D]).
-
-:- pred files(files::out, lines::in, lines::out) is multi.
-files([file(Name, Size) | Files]) -->
-  line([SSize, Name]), {to_int(SSize, Size)},
-  files(Files).
-files(Files) -->
-  line([Dir, _]), {Dir = "dir"},
-  files(Files).
-files([]) --> [].
+:- pred files(int::out, lines::in, lines::out) is multi.
+files(Size + Rest) -->
+  [Line], {to_int(head(words(Line)), Size)},
+  files(Rest).
+files(Size) -->
+  [Dir], {append("dir ", _, Dir)},
+  files(Size).
+files(0) --> [].
 
 :- pred dirs(dirs::out, lines::in, lines::out) is multi.
 dirs([D | Ds]) --> dir(D), dirs(Ds).
@@ -53,28 +38,20 @@ dirs([])       --> [].
 
 :- pred find(pred(dir)::(pred(in) is semidet), dir::in, list(dir)::out) is det.
 find(P, Dir, Out) :-
-  map(find(P), dirs(Dir), Outs),
-  Children = condense(Outs),
+  map(find(P), dirs(Dir), Outs), Children = condense(Outs),
   (if P(Dir) then Out = [Dir | Children] else Out = Children).
 
 :- pred size_lte(int::in, dir::in) is semidet.
-size_lte(Size, Dir) :- total(Dir) =< Size.
+size_lte(Size, Dir) :- size(Dir) =< Size.
 
 :- pred size_gte(int::in, dir::in) is semidet.
-size_gte(Size, Dir) :- total(Dir) >= Size.
+size_gte(Size, Dir) :- size(Dir) >= Size.
 
-:- func sort_size(list(dir)) = list(dir).
-sort_size(Dirs) = sort(func(D1, D2) = ordering(total(D1), total(D2)), Dirs).
+:- pred go(part::in, dir::in, int::out) is det.
+go(one, Top, sum(map(size, Found))) :-
+  find(size_lte(100_000), Top, Found).
+go(two, Top, det_head(sort(map(size, Found)))) :-
+  find(size_gte(size(Top) - 40_000_000), Top, Found).
 
-run(one, Lines, univ(Out)) :-
-  if dir(Top, Lines, []) then
-    find(size_lte(100_000), Top, Found),
-    Out = sum(map(total, Found))
-  else
-    die("bad input").
-run(two, Lines, univ(Out)) :-
-  if dir(Top, Lines, []) then
-    find(size_gte(total(Top) - 40_000_000), Top, Found),
-    Out = det_head(sort(map(total, Found)))
-  else
-    die("bad input").
+run(Part, Lines, univ(Out)) :-
+  if dir(Top, Lines, []) then go(Part, Top, Out) else die("bad input").