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', 'F', '4477', '1565', '4407', 'r', 'v', '7237', '83', '5243', 'O', 'z', 'W', '7703', 'Q', 'i', '9657', 'n']