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: ['7831', 'O', '6017', 'v', 'U', '5761', 'Q', 'Q', 'w', '8465', 'Z', 'P', 'i', 'u', '1635', 'n', '8471', '4213']

SOLUTION: 42393

PROBLEM: ['291', 'R', 'N', '983', '2879', 'C', '3797', '4837', '793', '5489', 'k', '535', 'L', '3605', 's', '3701', 'U', '4399', '2489', '4739']

SOLUTION: 38537

PROBLEM: ['Z', '9069', 'x', 'D', '7243', 'L']

SOLUTION:
16312