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: ['5715', 'r', 'R']

SOLUTION: 5715

PROBLEM: ['4271', 'N', 'M', '5239', '7037', 'x', 'U', 's', '7107', '4163', 'f', '3607', '6155']

SOLUTION: 37579

PROBLEM: ['g', 'N', 'U', '4531', '7443', '5953', 'y', '1359', '4025', 'r', 's', '8231']

SOLUTION:
31542