There is a large stream of numbers coming in such as 5 6 7 2 3 1 2 3 .. What kind of data structure is suitable for this problem given the constraints that elements must be inserted in descending order and duplicates should be eliminated.

I am not looking for any code just ideas? I was thinking of a Self-Balancing BST where we could add the condition that all nodes < current node on left and all nodes > current node on right, this takes care of the duplicates .. but i don't think they are necessarily inserted in descending order. Any ideas what might be a better choice .. ofcourse it needs to be efficient time and space wise.