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.
['5457', 'P', 'R', '3653', 'o', '7335', '2551', '7229', '3985', 'w', 'O', 'j', 'y', '5115', 'q', '1765', 'y', '1135', 'i']