s/^/\nz,/
:
s/[1-8]/&A/g
y/12345678/01234567/
s/A0/8AA/
t
s/0//g
s/,/<zabcdefghijklmnopq>,/
s/\(.\)<.*\1\(.\).*>/\2/
h
:1
s/\n\(.\)/\1&/
s/\<A/=/g
/A,.*A$/b1
y/=/A/
T
s/\(A*\)A,\1$/A,\1/
t
:3
P
s/A//
/A,/b3
g
s/\(,A*\)\1/\1,/
/,$/d
b