Map ← ⍥(⍉≡(⊂⊂⊙:.@.))2 ⊜∘≠@\n.&fras"10.in"
Inf ← 9999 # applied infinity
F ← +×Inf=0./+⊞=:Map
D ← F"|LJ"
U ← F"|7F"
R ← F"-J7"
L ← F"-FL"
M ← ↧+1×
TD ← M D ↻¯1.
TU ← M U ↻ 1.
TR ← M R≡↻¯1.
TL ← M L≡↻ 1.
T ← TU TL TD TR
-1/↥/↥×≠Inf⍢(T.⊙;)(¬≍)⊃∘(×0) F"S"