To learn the name of a key in HKN, press the key and look in HKN's upper right corner. But I'll save you some time:

<Hotkey ctrl alt shift R>

if you want to distinguish the left and right side keys so you can make two different hotkeys, you can do this instead:

<Hotkey Lctrl Lalt Lshift R>
<Hotkey Rctrl Ralt Rshift R>

(You don't have to capitalize the R's and L's that way -- I just did it for emphasis.)