#include <iostream>
#include <vector>
#include <set>
#include <climits>
#include <algorithm>
#include <string>
#include <cmath>
#include <queue>
#include <stack>

using namespace std;

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	int n;	cin >> n; n /= 10;
	string str;	cin >> str;
	int wyn = 0, c = 0;
	for (int i = 0; i < str.size(); i++) {
		if (str[i] == 'T')
			c++;
		if ((i+1) % n == 0) {
			if (c == n) {
				wyn++;
			}
			c = 0;
		}
	}
	cout << wyn;

	return 0;
}