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.
['u', '631', 'P', 'y', '8163', '39', '5693', 'o', 'W', '7601', 'U', 'v', '5411', 'Q', 'X', 'F', 'p', 'a', '3259', '1133']