~ "aoc.ua" ~ Lines

Input ← Lines &fras "input/day04.txt"
Wall  ← ≡◇=@@ Input

/⊂ -₁⇡[3 3]
▽¬⍜⍉(⊡1)⊸⦷0_0

/+ ⬚0˜↻ Wall
<4
×Wall
/+♭