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Score : $300$ points

问题陈述

这个问题中11/22字符串的定义与问题A和E中的定义相同。

如果一个字符串$T$满足以下所有条件，则称其为11/22字符串：

• $|T|$是奇数。这里，$|T|$表示$T$的长度。
• 第1个到第$(\frac{|T|+1}{2} - 1)$个字符都是1。
• 第$(\frac{|T|+1}{2})$个字符是/。
• 第$(\frac{|T|+1}{2} + 1)$个到第$|T|$个字符都是2。

例如，11/22、111/222和/是11/22字符串，但1122、1/22、11/2222、22/11和//2/2/211不是。

你给定了一个由1、2和/组成的长度为$N$的字符串$S$，其中$S$至少包含一个/。 找出$S$中一个（连续的）子串作为11/22字符串的最大长度。

以上为大语言模型 kimi 翻译，仅供参考。

Problem Statement

The definition of an 11/22 string in this problem is the same as in Problems A and E.

A string $T$ is called an 11/22 string when it satisfies all of the following conditions:

• $|T|$ is odd. Here, $|T|$ denotes the length of $T$.
• The $1$-st through $(\frac{|T|+1}{2} - 1)$-th characters are all 1.
• The $(\frac{|T|+1}{2})$-th character is /.
• The $(\frac{|T|+1}{2} + 1)$-th through $|T|$-th characters are all 2.

For example, 11/22, 111/222, and / are 11/22 strings, but 1122, 1/22, 11/2222, 22/11, and //2/2/211 are not.

You are given a string $S$ of length $N$ consisting of 1, 2, and /, where $S$ contains at least one /.
Find the maximum length of a (contiguous) substring of $S$ that is an 11/22 string.

Constraints

• $1 \leq N \leq 2 \times 10^5$
• $S$ is a string of length $N$ consisting of 1, 2, and /.
• $S$ contains at least one /.

Input

The input is given from Standard Input in the following format:

$N$

$S$

Output

Print the maximum length of a (contiguous) substring of $S$ that is an 11/22 string.

Sample Input 1

8
211/2212

Sample Output 1

5

The substring from the $2$-nd to $6$-th character of $S$ is 11/22, which is an 11/22 string. Among all substrings of $S$ that are 11/22 strings, this is the longest. Therefore, the answer is $5$.

Sample Input 2

5
22/11

Sample Output 2

1

Sample Input 3

22
/1211/2///2111/2222/11

Sample Output 3

7