sed ':
s/[1-9]/&_/g
y/123456789/012345678/
s/_0/9_/
t
s/\(_\+\) 0*\1\b/ \1-/
t
s/.*_/1/
:0
s/-/<<123456789-01>/
s/\(.\)<.*\1\(-*.\).*>/\2/
t0'