No one, please!

Burlesque, 10 bytes

{11~[n!}FO

Older versions:

ro{11~[n!}f[

ro{Sh"11"~=n!}f[

Bash + GNU utils, 36

seq $1$1|grep -v 11|sed -n "$1{p;q}"

Perl 5, 34 Bytes

Looping a counter and changing the occasional double-one.

map{$i++;$i=~s/11/12/}1..pop;say$i

Test

$ perl -M5.012 -e 'map{$i++;$i=~s/11/12/}1..pop;say$i' 111
$ 122