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# Definition for a binary tree node.
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# class TreeNode:
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#     def __init__(self, val=0, left=None, right=None):
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#         self.val = val
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#         self.left = left
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#         self.right = right
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class Solution:
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    def sumNumbers(self, root: Optional[TreeNode]) -> int:
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        int_list = []
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        def traverse(node, input_string):
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            nonlocal int_list
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            if not node:
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                return int_list
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            input_string = input_string + str(node.val)
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            if not (node.left or node.right):
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                int_list.append(int(input_string))
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            traverse(node.left, input_string)
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            traverse(node.right, input_string)
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        traverse(root, "")
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        return sum(int_list)