双端队列 C. Vasya and String

High school student Vasya got a string of length n as a birthday present. This string consists of letters 'a' and 'b' only. Vasya denotesbeauty 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?

Input

The first line of the input contains two integers n and k (1 ≤ n ≤ 100 000, 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.

Output

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

string s;
int main()
{
int n,k;
while(cin>>n>>k){
cin>>s;

int start = 0;
int ans = 0;
deque<int> De;
for(int i = 0;i < s.size();i ++){
if(s[i] == 'b') De.push_back(i);
if(De.size() > k){
start = De.front()+1;
De.pop_front();
}
ans = max(ans,i-start+1);
}
De.clear();
start = 0;
for(int i = 0;i < s.size();i ++){
if(s[i] == 'a') De.push_back(i);
if(De.size() > k){
start = De.front()+1;
De.pop_front();
}
ans = max(ans,i-start+1);
}
cout<<ans<<endl;
}
return 0;
}