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.

Example Input: ['291', 'R', 'N', '983', '2879', 'C', '3797', '4837', '793', '5489', 'k', '535', 'L', '3605', 's', '3701', 'U', '4399', '2489', '4739']
Example Output: 38537

Example Input: ['2871', '1337', '3771', '4671', 'l', '3785', 'V', 'z', 'R', 'u', '6097', 'R', '4297', 'd', '6339', 'Y', 'V', '5873', '7399']
Example Output: 46440

Example Input: ['3873', 'D', 'J', '2799', 'k', 'F', 'I', '3457', '5647', '4815', '7509', 'Y', '1251', '2211']
Example Output:
31562