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: ['r', '6537', '3001', '7879']

Answer: 17417


Question: ['Q', '1669']

Answer: 1669


Question: ['U', 'd', '3499', 'S', 'c', 'P', 'v', '5861', '625']

Answer:
9985