diff --git a/.gitignore b/.gitignore
index 3acba4b..fc5d555 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,4 +3,5 @@ session.key
 input
 .tup
 out
-*.im
\ No newline at end of file
+*.im
+vis/
\ No newline at end of file
diff --git a/days/day05.st b/days/day05.st
new file mode 100644
index 0000000..638fe5b
--- /dev/null
+++ b/days/day05.st
@@ -0,0 +1,58 @@
+Dictionary extend [
+    at: key inA: Type [^self at: key ifAbsentPut: [Type new]]
+    at: key inA: Type add: elt [ (self at: key inA: Type) add: elt ]
+]
+
+Object subclass: Ordering [
+    | beforeMap |
+    initialize [beforeMap := Dictionary new]
+
+    graphviz
+    [ AOC visualizeWithExt: '.dot' do: [
+              :stream |
+              stream << 'digraph {'.
+              beforeMap keysAndValuesDo: [
+                  :k :vs | vs do: [
+                      :v | stream << k << ' -> ' << v << ';'. ]].
+              stream << '}'.
+          ]]
+
+    order: page1 before: page2
+    [ beforeMap at: page2 inA: Set add: page1 ]
+    addRule: ruleStr
+    [ ruleStr scanf: '%d|%d' with: [ :x :y | self order: x before: y ] ]
+
+    isValid: man
+    [ | mustNotOccur | mustNotOccur := Set new.
+      man do: [
+          :elt |
+          (mustNotOccur includes: elt) ifTrue: [^false].
+          mustNotOccur addAll: (beforeMap at: elt inA: Set). ].
+      ^true ]
+
+    sort: man
+    [ ^man asSortedCollection: [ :x :y | ((beforeMap at: y) includes: x) ] ]
+]
+
+Collection extend [
+    middleElement [ ^self at: self size // 2 + 1 ]
+]
+
+AOC input: [ (stdin contents tokenize: (String with: $<10> with: $<10>))
+                 letArrayInBlock: [
+               :rules :seqs | | ord mans |
+               ord := Ordering new.
+               rules lines do: [ :rule | ord addRule: rule ].
+               mans := seqs lines collect: [
+                   :seq | seq chain tokenize: ','; collect: [:x | x asNumber] ].
+               "ord graphviz."
+               {ord . mans} ] ];
+    part1: [ :ord :mans | mans select: [ :man | ord isValid: man ] ];
+    part2: [ :ord :mans |
+             mans chain reject: [ :man | ord isValid: man ];
+                  collect: [ :man | ord sort: man ] ];
+    result: [ :ordAndMans :part |
+              part chain valueWithArguments: ordAndMans;
+                          collect: [:man | man middleElement];
+                          sum ];
+    finish.
diff --git a/days/utils.st b/days/utils.st
index 31688e9..0aa909c 100644
--- a/days/utils.st
+++ b/days/utils.st
@@ -22,10 +22,21 @@ AOC class extend [
     "TODO: save as an image?"
     finish
     [ | startTime stopTime |
+      (Smalltalk getenv: 'AOC_RUN') ifNil: [
+          stdout << 'AOC_RUN not set -- not running.'.
+          ^nil ].
       startTime := Time millisecondClock.
       self run.
       stopTime := Time millisecondClock.
       stdout << 'Time elapsed: ' << (stopTime - startTime) << 'ms'; nl. ]
+
+    visualizeWithExt: ext do: block
+    [ | file io |
+      file := (Smalltalk getenv: 'AOC_VIS') ifNil: [^nil].
+      file := (file,ext) asFile.
+      file printNl.
+      file parent createDirectories.
+      io := file writeStream. [ block value: io ] ensure: [io close] ]
 ]
 
 "--- Scanf ---"
diff --git a/run.sh b/run.sh
index c3dd0de..9811507 100755
--- a/run.sh
+++ b/run.sh
@@ -22,4 +22,7 @@ else
     fi
 fi
 
+export AOC_VIS="$DIR/vis/day$DAYP"
+export AOC_RUN=1
+
 exec gst -g "days/utils.st" "days/day$DAYP.st" < "$AOC_INPUT"