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: ['5573', '6221', 'C', '8649', '6603', 'q', '9403']

SOLUTION: 36449

PROBLEM: ['v', 't', 'a', 'r', 'O', 'I']

SOLUTION: 0

PROBLEM: ['5717', '1971', 'w', 'U', 'z', '747', 'u']

SOLUTION:
8435