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⎕ct←0
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i0←{⎕ct←0 ⋄ ⍺⍳⍵} x←?1e6⍴0 cmpx 'x⍳x' 'x i0 x' ⍝ selfie y←(⍴x)⍴x cmpx 'x⍳y' 'x i0 y' ⍝ not selfie