You are given an integer n.

Let's define s(n) as the string "BAN" concatenated n

times. For example, s(1) = "BAN", s(3) = "BANBANBAN". Note that the length of the string s(n) is equal to 3n.

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Consider s(n). You can perform the following operation on s(n)

any number of times (possibly zero):

Select any two distinct indices i and j (1≤i,j≤3n,i≠j).

Then, swap s(n)i and s(n)j.

You want the string "BAN" to not appear in s(n) as a subsequence. What's the smallest number of operations you have to do to achieve this? Also, find one such shortest sequence of operations.

A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.

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给定一个整数 n。

让我们将 s(n) 定义为字符串“BAN”连接 n

次。 例如，s(1) =“BAN”，s(3) =“BANBANBAN”。 请注意，字符串 s(n) 的长度等于 3n。

考虑 s(n)。 可以对 s(n) 执行以下操作

任意次数（可能为零）：

选择任意两个不同的索引 i 和 j (1≤i,j≤3n,i≠j)。

然后，交换 s(n)i 和 s(n)j。

您希望字符串“BAN”不作为子序列出现在 s(n) 中。 要实现这一目标，您需要执行的最少操作次数是多少？ 另外，找到一个这样的最短操作序列。

如果可以通过删除几个（可能是零个或全部）字符从 b 中获得 a，则字符串 a 是字符串 b 的子序列。

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主要是判断是奇数还是偶数，然后依次去交换即可。

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