diff --git a/aoc.bqn b/aoc.bqn
index 3f05432..428eeeb 100644
--- a/aoc.bqn
+++ b/aoc.bqn
@@ -26,9 +26,9 @@ Day3 ⇐ {
 
 Day4 ⇐ {
   Line ← •BQN∘> '‿'⍟(∊⟜"-,")¨ # hehe
-  A ← {a‿b‿c‿d:(∧´c‿b≥¨a‿d)∨∧´d‿a≥¨b‿c}
-  B ← {a‿b‿c‿d:(∧´c‿b≥¨a‿c)∨∧´a‿d≥¨c‿a}
-  +´˘⍉>((A⋈B)Line)¨•FLines𝕩
+  F ← {∨´∧´˘≥´⎉1(2¨↕3)⥊𝕩⊏˜𝕨-'a'}
+  A ← "cabddbac"⊸F, B ← "cabcacda"⊸F
+  +´(A⋈B)∘Line¨•FLines 𝕩
 }
 # ⟨ 536 845 ⟩
 # •Show Day4 ⊑•args