Merging local repositories

[Nikolaus Demmel]

Hey list,

I'm sorry if I ask a stupid question that is explained in some faq,  
but all my searches seem to lead to howtos of merging changes or  
repositories on some parent, which i dont use.

I use mercurial for local version-control. I have created 3  
repositories. One in /a/b/, one in /a/c/ and one in /a/ itsself  
(which includes /a/d/). How can I now merge the repositories in /a/b/  
and /a/c/ to the one in /a/, so that i'm left with only one  
repository and can commit all changes by calling $hg ci in /a/?

Thanks for you help.
Regards,
Niko