s/\(.\) \(.\) \(.\) \(.\) \(.\) \(.\)/\2\6-\3\5 \3\4-\1\6 \1\5-\2\4/
:
s/[1-9]/&a/g
y/123456789/012345678/
s/\Ba0a*/,,&,&/
s/\B0a*\|,..//
t
s/a-0a/-0/
t
:2
s/a/<<123456789a01>/
s/\(.\)<.*\1\(a*.\).*>/\2/
t2
s/-0//g
s/0-/-/g