Maximum Value

- 给定一个序列 $a_i$，请找出两个数 $i,j$，使得 $a_i \ge a_j$，并且使得 $a_i \bmod a_j$ 的值最大，求这个 $a_i\bmod a_j$ 的最大值。 - 对于 $100\%$ 的数据，$1 \le n \le 2\times 10^5$，$1 \le a_i \le 10^6$。 - Translated by 一只书虫仔 & QwQcOrz。

You are given a sequence $ a $ consisting of $ n $ integers. Find the maximum possible value of  (integer remainder of $ a_{i} $ divided by $ a_{j} $ ), where $ 1<=i,j<=n $ and $ a_{i}>=a_{j} $ .

You are given a sequence $ a $ consisting of $ n $ integers. Find the maximum possible value of  (integer remainder of $ a_{i} $ divided by $ a_{j} $ ), where $ 1<=i,j<=n $ and $ a_{i}>=a_{j} $ .

Print the answer to the problem.

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