permalink with only the last category

Hi,
I use /%category%/%postname% in my blog wordpress (3.0.3)

If I have a post that is in the category “cat-1”, which is in category “maxcat-a”, which is in category “maxmaxcat-x”, its permalink is:
“blogname/maxmaxcat-x/maxcat-a/cat-1/postname”

I would like permalink as:
“blogname/cat-1/postname”
is possible?

I have found a plugin for modified the permalink in
“blogname/maxmaxcat-x/postname” but not is that I want.
I want only the last category and not the others.

Do you know some plugin that work for this?

Thanks

P.S. Sorry for my english, I don’t speak english very well