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class Solution:
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    def sumEvenGrandparent(self, root: TreeNode) -> int:
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        def dfs(root, p, gp):
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            if not root:
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                return 0
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            if gp and gp.val % 2 == 0:
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                return root.val + dfs(root.left, root, p) + dfs(root.right, root, p)
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            return 0 + dfs(root.left, root, p) + dfs(root.right, root, p)
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        return dfs(root, None, None)