sed ':
s/[1-9]/&s/g
y/123456789/012345678/
s/s0/9s/
t
s/0*s\{7\}//
/s\{8\}/!s/.*/-1/
:1
s/s/<<123456789s01>/
s/\(.\)<.*\1\(s*.\).*>/\2/
t1'