#include <iostream>
#include <string>
using namespace std;

int main() {
    int n,k;
    cin >> n >> k;
    string s;
    cin >> s;
    
    int cnt = 0;
    for (int i = 0;i < n;i++) {
        if (s[i] == 'P') {
            for (int j = -k;j <= k;j++) {
                if (s[i+j] == 'P') continue;
                if (s[i+j] == 'H' && s[i+j] != 'X') {
                    s[i+j] = 'X';
                    cnt++;
                    break;
                }
            }
            
        }
    }
    cout << cnt;
    return 0;
}