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

SOLUTION: 38537

PROBLEM: ['b', 's', 'v', '4757', '9063', 'I', '8397', '7975', 'Q']

SOLUTION: 30192

PROBLEM: ['3477', 'j', 'R']

SOLUTION:
3477