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

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

int main() {
    registerValidation();
    ll N = inf.readLong(MIN_N, MAX_N);
    inf.readEoln();
    set<char> st={'C', 'P', 'T', 'F'};
    string cpctf = "";
    string cpctcpc = "";
    int ans = 0;
    for(int i = 0; i < N; i++){
        char c = inf.readChar();
        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();
        }
    }
    inf.readEoln();
    cout << ans << endl;
    inf.readEof();
}