( + )* . zip2 . ((+)*.zip2.(select.(id,(+)*.zip2.(iota.-.(#,2)o,repeat.(1,-.(#,2)o)o)o)o,select.(id,(-)*.zip2.((+)*.zip2.(iota.-.(#,2)o,repeat.(1,-.(#,2)o)o)o,repeat.(1,-.(#,2)o)o)o)o)o,select.(id,(+)*.zip2.((+)*.zip2.(iota.-.(#,2)o,repeat.(1,-.(#,2)o)o)o,repeat.(1,-.(#,2)o)o)o)o)o