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.

Example Input: ['j', 'f', '3831', 'B', 'D']
Example Output: 3831

Example Input: ['4201', '6445', '4009', 'q']
Example Output: 14655

Example Input: ['6909', '2793', '2763', 'I', '6431']
Example Output:
18896