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: ['K', '479', 'u', '3489', 'o', '9589', '7153', '7649', '123', 'a', 'A', '3951', '847', 'N', 'R', '947', '9243', 'G', 'a']

SOLUTION: 43470

PROBLEM: ['1875', '9833', 'i', '7493', 'J', 'P', 'z']

SOLUTION: 19201

PROBLEM: ['3839', 'M', 'J', '7869', '2957', '4011', 'w', 'f', '3391', 'y', '5407', 't', 's']

SOLUTION:
27474