B - A and B and Compilation Errors

最新推荐文章于 2023-03-15 15:42:48 发布

ACMer_hades

最新推荐文章于 2023-03-15 15:42:48 发布

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分类专栏：模拟题文章标签： acm 模拟题数学题

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本文讲述了A和B两位程序员在准备编程比赛时遇到的错误修复问题，以及他们在组建训练团队时如何优化成员分配以最大化知识分享的效果。在错误修复中，他们需要找出在两次编译后消失的两个错误。在团队构建中，A主张1个老手带2个新手，B则认为2个老手带1个新手更优。问题转化为在有限的老手和新手中，如何最大化团队数量。

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A and B are preparing themselves for programming contests.

B loves to debug his code. But before he runs the solution and starts debugging, he has to first compile the code.

Initially, the compiler displayed n compilation errors, each of them is represented as a positive integer. After some effort, B managed to fix some mistake and then another one mistake.

However, despite the fact that B is sure that he corrected the two errors, he can not understand exactly what compilation errors disappeared — the compiler of the language which B uses shows errors in the new order every time! B is sure that unlike many other programming languages, compilation errors for his programming language do not depend on each other, that is, if you correct one error, the set of other error does not change.

Can you help B find out exactly what two errors he corrected?

Input

The first line of the input contains integer n (3 ≤ n ≤ 10⁵) — the initial number of compilation errors.

The second line contains n space-separated integersa₁, a₂, ..., a_n (1 ≤ a_i ≤ 10⁹) — the errors the compiler displayed for the first time.