title: Problem 832
date: 2023/03/05 04:00:00
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# [Problem 832](https://projecteuler.net/problem=832)
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[Xem đề gốc (tiếng Anh)](https://projecteuler.net/problem=832)

## **Dãy Mex**

$a_0 = 0$, $a_n = \text{mex}(\{a_0,\ldots,a_{n-1}\} \text{ XOR})$. Tính $a(10^{18}) \pmod{10^9+7}$.

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