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.

['K', '4403', 'a', '3881', '4139', 'w', '1861', 'G']
14284

['z', 'E', 'u', '4437', '7767']
12204

['7817', '9723', '3509', 'l', 'n']

21049