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.

['6921', 'a', 'U', '2821', '2111', 'h', '3937', '3697', 'd', '6309', 'q', '7961', '5287', '5375', '2721', '4523', 'V', '8633', 'c', '7643']
67939

['j', 'f', '3831', 'B', 'D']
3831

['i', '1479', 'k', 'q', 'm', '2497', 'E', 't', '2113', '6573', '3659', 'D', '3953']

20274