﻿
 (X⌷⍨⊂⍵) ≢⍤¯1 999 ⊢(X⌷⍨⊃⍵)

 (X⌷⍨⊂⍵) ≢⍤¯1 ∞ ⊢(X⌷⍨⊃⍵)
