#include <bits/stdc++.h>
using namespace std;
int arr[26];
int main() {
	int n,k,x,count = 1,mx = 0,c;
	string str;
	cin >> n >> k >> str;
	if(k == 1){
		for(int i = 0;i < n;i++){
				c = str[i] - 97;
				arr[c]++;
				mx = max(mx,arr[c]);
			}
	}
	else{
		for(int i = 0;i < n - 1;i++){
			if(str[i] == str[i + 1]){
				count++;
				if(count == k){
					c = str[i] - 97;
					arr[c]++;
					mx = max(mx,arr[c]);
					count = 1;
					i++;
				}

			}
			else if(count > 1)
				count = 1;
		}
	}
	cout << mx;
}