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: ['g', 'A', 'r', '539', '5459', '2725', '7447', '3693', '1757', 'r', 'W', '5949', '4569', '5153', '3985', 'Q', '505', 'M', '8989']
Example Output: 50770

Example Input: ['5715', 'r', 'R']
Example Output: 5715

Example Input: ['2471', 'J', '5779', 'a']
Example Output:
8250