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: ['9403', '2607', 'G', '7901', 'K', '7967', 'a', 'n', '1967', 'x', 'g', '1081']

SOLUTION: 30926

PROBLEM: ['Y', '9053', 'N', '6921']

SOLUTION: 15974

PROBLEM: ['793', 'c']

SOLUTION:
793