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?

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.

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;
}