Question regarding sharing cookies across sites

[OG]

Hello,

I would like to share cookies across various web based apps, and
from what I understand your apps can do this as long as they all belong
to the same domain. For example app1.mydomain.com can share cookies
with app2.mydomain.com, as long as you specify ".mydomain.com" as the
cookie's domain.

However, I'm trying to share cookies in an environment where the
domains are more like app1.A.mydomain.com and app2.B.mydomain.com. It's
not clear to me if I can simply specify".mydomain.com" as the domain,
or if this will not work because the ".A" and ".B" are also considered
part of the domain.

Your help would be much appreciated.

Thanks,
Attila