Best I can come up with is {."1 ((] , -. {~ {. at I.@(-. +./"1 at e. {:@]))^:(<:@#@[) ,:@{.) edges 1 3 17 18 18 20 20 21 22 14 15 16 23 26 25 13 12 11 11 10 9 7 6 5 4 2 Change {. at I. to {:@I. if you want things in the other order. -- Raul