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.

['J', 'm', '1255', 'S']
1255

['2787', 'z', '9351', '3339']
15477

['2633', 'K', '3135', '8493', 'i', '8515', 'Q', 'U']

22776