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.

['4869', 'L']
4869

['V', '8137', 'b', 'k', '2081', 'L', '9733', '7525', 'D', '2381', 'O']
29857

['W', 'H', 'k', 'L', '2425']

2425