How to get upper category hierarchies of an item?

Hello;

I have an item 00000003100, this item has the following category hierarchy Main>Subcat>Subcat2>Subcat3.

When I use a simple code as follows:

invTbl = InventTable::find("00000003100");
info(strfmt("%1",invTbl.categoryName()));

I always get the last category as Subcat3 in my example.How can I get the upper categories by code?

I would like to get Main or Subcat2 categories for example.

Regards