Please help me to find a CSS selector

Hi there!

On https://campus.ichblogge.com/lektionen/3-gastgeber-blogs/ you see a sidebar with navigation items. If you toggle the first item of that list (click to toggle icon), you should get a better look of the 10 category elements of the navigation: http://screencast.com/t/4YKVaWqVy

Now I want to hide a few of this items, one by one. (I spare you the reason why I need this workaround)

I found that this code hides the FIRST category of that navigation.

.apw>div:first-child a {
    border-top: 0px;
    display: none;
}

But I cant find the code to hide for example the second, third, or fourth (and so on) category.
(and I don't understand why its so hard for me to find these, while I found the first quickly)

Can anyone help me out here?