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.
['m', 'J', '7617', 'm', '935', 'L', 'n', '7503', 'r', '1345', 'i', '6609', 'G', '3787', '309', '8365', 'x', 'i', 'i', '2043']