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.
['d', '7619', '7311', 'S', '3797', 'Y', '5053', 'P', '6303', '3119', '4865', 'y', 'N', 'U', 'Z', '3771', '265', 'c', '991']