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: ['4975', 'M', 'C', 'D', 't', 'i', 't', 'L']
Example Output: 4975

Example Input: ['S', 'D', '3101', '4967', '8197', '5025', '4257', 'S', 'X', '7641', 'n', '6775', '4719', 'o', '2821', 'x', '5605', '2181']
Example Output: 55289

Example Input: ['6787', 'W', 'I', '4929', 'j', 'I', '3487', 'F', '3927', 'Q', 's', 'X', '9939', 'n']
Example Output:
29069