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