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.
['i', '3741', '8305', 'K', '2591', 'Y', '6587', '6115', '5187', '7295', '7585', '389', 'c', '1081', '8577', '4481', '8397', 'L', '3437']