Data Storage with Last Accessed Key

Design a data storage system supporting the following operations: put(K k, V v): Store the pair (k, v) in the system. get(K k): Return the value associated with key k. last(): Return the most recently accessed key. delete(K k): Remove the key k and its associated value from the system. Example: put("a", 1) put("b", 2) get("a") last() # returns "a" delete("a") last() # returns "b" Example Input put a 1 put b 2 get a last delete a last