s/./1  ABCDEF&EDCBA  1/
s/C.*5.*B\|F8E\|9//
h
:
s/\(.\).\1/\1/
y/12345678/23456789/
s/.*/1&1/
x
G
x
G
h
s/\n.*//
/ /b
x
y/ABCDEF/123456/