Permalnks problem

Hello

I have a question about permalnks in Wordpress

Now I have structure: /%category%/%postname%/

But I would like to have thid kind of structure Category/subcategory/postname,
but subcategory is not the right name, for permalnks to take subcategories?
Which is the right name so my website would have that kind of url.

I would like to have For example Sitepoint.com/forum/seo/permalinks-problem
Now i have for example Sitepoint.com/forum/permalinks-problem

I have it: /%category%/%child-category%/%postname%/

Thanks anyway