In this task, you are given an input list A. You need to find all the elements of the list that are numbers and calculate their sum.
['N', '1393', 'J', 'g', 'X', 'f', '4955', '3997', '1999', 'C', 'z', '3083', '253', '5865', '5331', '6941', '9297', 'q', 'L', 'L']