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: ['N', '1337', 'C', 'T', '863', 'j', '2369', 'P', 'A', 'x', '5725', '2333', 'Q', '9149', 'Q', '8529', 'N']

SOLUTION: 30305

PROBLEM: ['211', '7561', '8725', '6139', 'I', '6585', '4231', 't', '2983', 'T', 'S', '9569', 'R', 'b', 'N', 'X', '9009']

SOLUTION: 55013

PROBLEM: ['3401', 'A', 'A', '261', '955', '903']

SOLUTION:
5520