A kind of counter in sed

/^[[:digit:]][[:digit:]]*$/!n;         # the line must contain only digits
x;s/.*//;x;                            # clear the hold space
: add
/9$/{s/9$//;x;s/.*/0&/;x;b add;};      # eliminate the last 9 from the p.s.
                                       # and add a 0 in front of the h.s.
s/8$/9/
s/7$/8/
s/6$/7/
s/5$/6/
s/4$/5/
s/3$/4/
s/2$/3/
s/1$/2/
s/0$/1/
s/^$/1/
G;s/\n//g;            # add the content of the h.s to the p.s