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.
['655', '9167', 'W', 'D', '7489', 's', 'G', '5731', 'p', 'n', '2829', '4355', '2221', '9251', 'R', '8259', '619', 'v', '2655', 'a']