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.
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Question: ['J', 'm', '1255', 'S']

Answer: 1255


Question: ['u', 'W', '1561', '9243', '4923', '9385']

Answer: 25112


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

Answer:
5715