Vasya and String

题意翻译

给你一个n个字符a与b组成的字符串，求至多改动k个字符后连续相同字符个数的最大值。

题目描述

High school student Vasya got a string of length $ n $ as a birthday present. This string consists of letters 'a' and 'b' only. Vasya denotes beauty of the string as the maximum length of a substring (consecutive subsequence) consisting of equal letters. Vasya can change no more than $ k $ characters of the original string. What is the maximum beauty of the string he can achieve?

输入输出格式

输入格式

The first line of the input contains two integers $ n $ and $ k $ ( $ 1<=n<=100000,0<=k<=n $ ) — the length of the string and the maximum number of characters to change. The second line contains the string, consisting of letters 'a' and 'b' only.

输出格式

Print the only integer — the maximum beauty of the string Vasya can achieve by changing no more than $ k $ characters.

输入输出样例

输入样例 #1

4 2
abba

输出样例 #1

4

输入样例 #2

8 1
aabaabaa

输出样例 #2

5

说明

In the first sample, Vasya can obtain both strings "aaaa" and "bbbb". In the second sample, the optimal answer is obtained with the string "aaaaabaa" or with the string "aabaaaaa".