Change Set List to Tree List

I tried to change the left list Structure (I guess {…,…,…} is a Set) to a Tree List like on the rigt (not only for the first 3 index like in the image) sorted by Value (a>b>c) but no sucess and i found no informations about using SETS nodes.

Hi,
try something like this:

Thanks a lot text was the right solution to manipulate the structure.
I had only to sort and cull the the rest, thanks again.