diff --git a/12/part2.naive.pl b/12/part2.naive.pl
new file mode 100644
index 0000000..f11f0af
--- /dev/null
+++ b/12/part2.naive.pl
@@ -0,0 +1,63 @@
+:- use_module(library(pio)).
+:- use_module(library(dcg/basics)).
+:- initialization(main, main).
+:- table nbads/2.
+:- table bads_or_unks/1.
+% :- table resolve/3.
+
+test :- main(['test.txt']).
+
+main([FileName | _]) :-
+    input(FileName, Lines),
+    % TrySolve = [Line-Bads, Prev, Curr]>>(
+    %     writef('%t, %t', [Line, Bads]),
+    %     resolve(Line, Bads, N),
+    %     Curr is Prev + N,
+    %     writef(' --> %t\n', [N])),
+    % foldl(TrySolve, Lines, 0, Ns),
+    TrySolve = [Line-Bads, N]>>(
+        resolve(Line, Bads, N), 
+        writef('%t <-- %t, %t\n', [N, Line, Bads])),
+    concurrent_maplist(TrySolve, Lines, Ns),
+    sum_list(Ns, Count),
+    writef('\nRes=%w, %w\n', [Ns, Count]).
+    
+% Bads is list of contiguous blocks of bad items in Xs; w/unks resolved in Y.
+resolve([], [], 1).
+resolve([good|Xs], Bads, Y) :- resolve(Xs, Bads, Y).
+resolve([unk|Xs], Bads, Y) :-
+    convlist({Xs, Bads}/[Choice, Yx]>>(resolve([Choice|Xs], Bads, Yx)),
+             [good, bad], Ys),
+    sum_list(Ys, Y).
+resolve([bad|Xs], [N|Bads], Y) :-
+    length(BadsUnks, N),
+    append(BadsUnks, [Next|RemainingXs], [bad|Xs]),
+    (Next = good; Next = unk),
+    bads_or_unks(BadsUnks),
+    resolve(RemainingXs, Bads, Y).
+
+% List contains all bads or unks
+bads_or_unks([]).
+bads_or_unks([bad|List]) :- bads_or_unks(List).
+bads_or_unks([unk|List]) :- bads_or_unks(List).
+    
+% List contains exactly N bad items.
+nbads([], 0).
+nbads([bad|List], N) :- N > 0, Remain is N - 1, nbads(List, Remain).
+
+% read input file into [(good;bad;unk)]-[list of bad runs]
+input(FileName, Lines) :- phrase_from_file(lines(Lines), FileName).
+
+lines([]) --> eos.
+lines([Status-Parity|Lines]) -->
+    (status(S), {append([S, [unk], S, [unk], S, [unk], S, [unk], S, [good]], Status)}),
+    (parity(P), {append([P, P, P, P, P], Parity)}),
+    lines(Lines).
+
+status([]) --> " ".
+status([good|Cdr]) --> ".", status(Cdr).
+status([bad|Cdr]) --> "#", status(Cdr).
+status([unk|Cdr]) --> "?", status(Cdr).
+
+parity([N]) --> number(N), ("\n"; eos).
+parity([N|Cdr]) --> number(N), ",", parity(Cdr).