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.
['3719', 'Z', 'M', '5741', '9943', '6825', 'S', '3917', '63', '205', '9155', 'K', '8579', '2335', 'O', '5401', '919', 'i', '603']