TASK DEFINITION: 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.
PROBLEM: ['n', 'W', '565', '6625', '903', 'o', '7995', '8339', '5251', 'e', 'a', '1081', '5813', 'o']

SOLUTION: 36572

PROBLEM: ['7459', '491', '7823', '6965', 'H', '109', 'R', 't', '3959', '2821', 'R', '2807', 'o', 'v', '1305', 'a', '1411', 'r', '3669']

SOLUTION: 38819

PROBLEM: ['R', 'r', '6393', 'f']

SOLUTION:
6393