#include <bits/stdc++.h>
using namespace std;
int main() {
int n,k;
string str;
cin>>n>>k;
cin>>str;
int i = 0 , j = 0;
multiset<char>ms;
int maxi = 0;
while(j<n){
ms.insert(str[j]);
char a = *ms.begin();
char b = *ms.rend();
while((b-a)>k){
ms.erase(str[i]);
i++;
a = *ms.begin();
b = *ms.rend();
}
maxi = max(maxi,(j-i+1));
j++;
}
cout<<maxi<<endl;
return 0;
}
I2luY2x1ZGUgPGJpdHMvc3RkYysrLmg+CnVzaW5nIG5hbWVzcGFjZSBzdGQ7CgppbnQgbWFpbigpIHsKCWludCBuLGs7CglzdHJpbmcgc3RyOwoJY2luPj5uPj5rOwoJY2luPj5zdHI7CglpbnQgaSA9IDAgLCBqID0gMDsKCW11bHRpc2V0PGNoYXI+bXM7CglpbnQgbWF4aSA9IDA7Cgl3aGlsZShqPG4pewoJCW1zLmluc2VydChzdHJbal0pOwoJCWNoYXIgYSA9ICptcy5iZWdpbigpOwoJCWNoYXIgYiA9ICptcy5yZW5kKCk7CgkJd2hpbGUoKGItYSk+ayl7CgkJCW1zLmVyYXNlKHN0cltpXSk7CgkJCWkrKzsKCQkJYSA9ICptcy5iZWdpbigpOwoJCQliID0gKm1zLnJlbmQoKTsKCQl9CgkJbWF4aSA9IG1heChtYXhpLChqLWkrMSkpOwoJCWorKzsKCX0KCWNvdXQ8PG1heGk8PGVuZGw7CglyZXR1cm4gMDsKfQ==