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.
--------
Question: ['4869', 'L']

Answer: 4869


Question: ['6787', 'W', 'I', '4929', 'j', 'I', '3487', 'F', '3927', 'Q', 's', 'X', '9939', 'n']

Answer: 29069


Question: ['5415', 'f', '3855']

Answer:
9270