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.
['N', '1303', 'g', '3851', '3879', 'p', 'P', '3685', 'A', 'i', 'c', 'X', '7113', 'e', 'u', 'V', 'z', '4943', 'F', 'm']