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.
['8231', 'H', 'd', '8535', '8949', 'i', '525', '8275', '7557', '6187', '2469', '5347', 'K', '7655', 'B', '4817', 'O', 'A']