CF145E.Lucky Queries

Petya loves lucky numbers very much. Everybody knows that lucky numbers are positive integers whose decimal record contains only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

Petya brought home string s with the length of n. The string only consists of lucky digits. The digits are numbered from the left to the right starting with 1. Now Petya should execute m queries of the following form:

• switch l r — "switch" digits (i.e. replace them with their opposites) at all positions with indexes from l to r, inclusive: each digit 4 is replaced with 7 and each digit 7 is replaced with 4 (1 ≤ l ≤ r ≤ n);
• count — find and print on the screen the length of the longest non-decreasing subsequence of string s.

Subsequence of a string s is a string that can be obtained from s by removing zero or more of its elements. A string is called non-decreasing if each successive digit is not less than the previous one.

Help Petya process the requests.

佩佳非常喜欢幸运数字。众所周知，幸运数字是指十进制表示中仅包含幸运数字 4 和 7 的正整数。例如，47、744、4 是幸运数字，而 5、17、467 则不是。

佩佳带回家一个长度为 $n$ 的字符串 $s$。该字符串仅由幸运数字组成。字符串中的字符从左到右编号，起始编号为 1。现在佩佳需要执行 $m$ 个如下形式的查询：

• switch l r — 将所有下标在区间 $[l, r]$（含端点）内的字符“翻转”（即替换为其相反数字）：每个数字 4 被替换为 7，每个数字 7 被替换为 4（其中 $1 \le l \le r \le n$）；
• count — 找出并输出字符串 $s$ 的最长非递减子序列的长度。

字符串 $s$ 的子序列是指通过从 $s$ 中删除零个或多个字符后所得到的字符串。若一个字符串中每个后续数字都不小于前一个数字，则称其为非递减字符串。

请帮助佩佳处理这些查询。

The first line contains two integers n and m (1 ≤ n ≤ 106, 1 ≤ m ≤ 3·105) — the length of the string s and the number of queries correspondingly. The second line contains n lucky digits without spaces — Petya's initial string. Next m lines contain queries in the form described in the statement.

第一行包含两个整数 $n$ 和 $m$（$1 ≤ n ≤ 10^6$，$1 ≤ m ≤ 3·10^5$）—— 分别表示字符串 $s$ 的长度和查询的数目。
第二行包含 $n$ 个幸运数字（不含空格）—— 这是 Petya 的初始字符串。
接下来的 $m$ 行，每行包含一个按题面描述格式给出的查询。

For each query count print an answer on a single line.

对于每个查询 count，在单独一行输出答案。

In the first sample the chronology of string s after some operations are fulfilled is as follows (the sought maximum subsequence is marked with bold):

1. 47
2. 74
3. 74

In the second sample:

1. 747
2. 447
3. 447
4. 774
5. 774

在第一个样例中，字符串 $s$ 在执行若干操作后的演变过程如下（所求的最大子序列用粗体标出）：

1. 47
2. 74
3. 74

在第二个样例中：

1. 747
2. 447
3. 447
4. 774
5. 774