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.
['L', 'a', '197', '2135', '271', 'p', '7215', '9653', 'y', 'c', 'A', '6959', 'A', '5749', 'W', '7259', '3797', 'R', 'x']