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class Solution:
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    def getDirections(
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        self, root: Optional[TreeNode], startValue: int, destValue: int
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    ) -> str:
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        def find(n: TreeNode, val: int, path: List[str]) -> bool:
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            if n.val == val:
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                return True
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            if n.left and find(n.left, val, path):
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                path += "L"
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            elif n.right and find(n.right, val, path):
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                path += "R"
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            return path
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        s, d = [], []
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        find(root, startValue, s)
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        find(root, destValue, d)
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        while len(s) and len(d) and s[-1] == d[-1]:
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            s.pop()
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            d.pop()
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        return "".join("U" * len(s)) + "".join(reversed(d))