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class Solution:
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    def numWaterBottles(self, a: int, b: int) -> int:
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        def sol(a, b, e, res):
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            if a != 0:
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                res += a
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            if (a + e) < b:
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                return res
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            a += e
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            new = a // b
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            e = a - (new * b)
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            a = new
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            return sol(a, b, e, res)
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        return sol(a, b, 0, 0)