#include <iostream>
#include <string.h>

using namespace std;

int countCorrect(string str, int n) {
    int corSize = n / 10;
    int res = 0;
    int x = 0;
    for(int i = 0; i < str.length(); ++i) {
        if (str[i] == 'T') {
            ++x;    
        }
        if ((i + 1) % corSize == 0) {
            if (x == corSize)
                res++;
            x = 0;
        }
    }
    return res;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    string a;
    int n;
    cin >> n >> a;
    printf("%d", countCorrect(a, n));
    return 0;
}