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.
['y', 'k', '9195', 'S', 'U', 'k', 'v', '7253', 'a', '7373', 'V', '3251', 'b', 'g', '8327', '8381', 'O', 'n']