#include <bits/stdc++.h>
using namespace std;
using ll = long long;

const ll MIN_N = 5;
const ll MAX_N = 500000;

int main() {
	ll N;
	cin >> N;
	string S;
	cin >> S;
	set<char> st = {'C', 'P', 'T', 'F'};
	string cpctf = "";
	string cpctcpc = "";
	int ans = 0;
	for (char c : S) {
		assert(st.count(c));
		cpctf += c;
		cpctcpc += c;
		if (cpctf.size() > 5) cpctf.erase(cpctf.begin());
		if (cpctcpc.size() > 7) cpctcpc.erase(cpctcpc.begin());
		if (cpctf == "CPCTF" || cpctcpc == "CPCTCPC") {
			ans++;
			cpctf.clear();
			cpctcpc.clear();
		}
	}
	cout << ans << endl;
}