Sorry, cut and paste should be double-checked ;-) <snip> The examples for a(4) (I hope I got it right - no l4a.jpg should be l5a.jpg) http://www.randomwalk.de/shoelace/l5a.jpg -1 5 4 B(1 5) -6 A(1 5) -3 B(1 5) 7 A(1 5) 2 B(1 5) 8 Hugo Pfoertner