#include <iostream>
#include <algorithm>
#include <math.h>
#include <vector>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <numeric>
#include <iomanip>

constexpr int MAX_INT = 2147483647;
constexpr int MIN_INT = -2147483648;

#define rep(n, a, b) for (int (n) = (a); (n) < (b); (n)++)
#define rrep(n, a, b) for (int (n) = (a); (n) >= (b); (n)--)
#define llrep(n, a, b) for (long long (n) = (a); (n) < (b); (n)++)
#define llrrep(n, a, b) for (long long (n) = (a); (n) >= (b); (n)--)
#define itrAll(x) (x).begin(), (x).end()
#define inputvec(v) for (auto& x : v) {std::cin >> x;}
using namespace std;

using uint = unsigned int;
using ushort = unsigned short;
using byte = unsigned char;
using ll = long long;
using ull = unsigned long long;
using ldouble = long double;
using ipair = pair<int, int>;
using llpair = pair<long long, long long>;

int main() {
    int N;
    string S;
    cin >> N >> S;

    vector<ipair> cpc; // { 開始インデックス, 繰り返し回数 }
    rep(i, 0, N - 2) {
        if (S[i] == 'C') {
            int r_cnt = 0;
            for (int j = i + 1; j < N - 1; j += 2) {
                if (S[j] == 'P' && S[j + 1] == 'C') {
                    r_cnt++;
                }
                else {
                    break;
                }
            }

            if (r_cnt) {
                cpc.push_back({ i, r_cnt });
                i += (r_cnt << 1);
            }
        }
    }

    if (!cpc.size()) {
        cout << 0 << endl;
        return 0;
    }

    /// <summary>
    /// [i] := {
    ///     [first]: i+1番目のCPC...PCまでの部分文字列のうち, 少なくともi番目の「最後の」CPCを変換したときのCPCTFの個数の最大値.
    ///     [second]: 〃のうち, i番目のCPCを変換していないときの〃.
    /// }
    /// </summary>
    vector<ipair> cnt(cpc.size());
    cnt[0] = { 0,0 };

    for (int i = 1; i < cpc.size(); i++) {
        auto& prev = cpc[i - 1];
        auto& current = cpc[i];
        ipair prevIdx = { prev.first, prev.first + (prev.second << 1) }, currentIdx = { current.first, current.first + (current.second << 1) };

        int margin = currentIdx.first - prevIdx.second - 1;

        if (margin == 1 && S[currentIdx.first - 1] == 'T') { // [..CPC]T[CPC..]
            if (current.second <= 2) {
                cnt[i] = { cnt[i - 1].second + 1, max(cnt[i - 1].first, cnt[i - 1].second) };
            }
            else {
                int v = max(cnt[i - 1].first, cnt[i - 1].second + 1);
                cnt[i] = { v,v };
            }
        }
        else if (margin >= 2 && S[prevIdx.second + 1] == 'T' && S[prevIdx.second + 2] == 'F') { // [..CPC]TF..[CPC..]
            int v = max(cnt[i - 1].first, cnt[i - 1].second + 1);
            cnt[i] = { v,v };
        }
        else { // [..CPC][CPC..] or [..CPC]..[CPC..]
            int v = max(cnt[i - 1].first, cnt[i - 1].second);
            cnt[i] = { v,v };
        }
    }

    auto& lastCpc = *(cpc.end() - 1);
    ipair lastIdx = { lastCpc.first, lastCpc.first + (lastCpc.second << 1) };
    auto& c = *(cnt.end() - 1);
    if (lastIdx.second + 2 < N && S[lastIdx.second + 1] == 'T' && S[lastIdx.second + 2] == 'F') {
        cout << max(c.first, c.second + 1) << endl;
    }
    else {
        cout << max(c.first, c.second) << endl;
    }

    return 0;
}