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.

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

['Q', '1669']
1669

['N', 'P', '1139', '4179', '4105', '4161', 'u', 'a', '9137']

22721