#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n;
  string s;
  cin >> n >> s;
  string t = "";
  int ans = 0;
  for (char c : s) {
    t += c;
    if (t.size() >= 5 && t.substr(t.size() - 5) == "CPCTF") {
      ans++;
      rep(_, 5) t.pop_back();
    }
    if (t.size() >= 7 && t.substr(t.size() - 7) == "CPCTCPC") {
      ans++;
      rep(_, 7) t.pop_back();
    }
  }
  cout << ans << endl;
  return 0;
}