Design a data structure D that can store integers. The data structure should be ale to store a multi-set, i.e. an element can appear multiple times. The data structure should support the following operations in O(log n) time, where n is the number of distinct integers stored in D . add(x): Adds/inserts integer a into D. Even if a belongs to D, r should still be added. frequency(x): Number of times a appears in D. . search(x): Returns true if is in D order (y): Number of elements in D that are larger than y. The element y may or may not be in D If you are using BST and would like to balance the tree, you may simply write balance and assume that this operation will take O(log n) time. Analyze the worst-case run time of the operations