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class Solution:
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    def getHappyString(self, n: int, k: int) -> str:
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        ans = []
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        letters = ["a", "b", "c"]
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        def happystr(n, prev, temp):
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            if n == 0:
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                ans.append("".join(temp))
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                return
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            for l in letters:
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                if l != prev:
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                    happystr(n - 1, l, temp + [l])
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        happystr(n, "", [])
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        if len(ans) < k:
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            return ""
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        return ans[k - 1]