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: ['6731', 'f', '4561', '5601', 'i']

SOLUTION: 16893

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

SOLUTION: 38819

PROBLEM: ['Y', 'R', 'y', '5447', 'o', '821']

SOLUTION:
6268