#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main() {
  int n;
  string s;
  cin >> n >> s;
  int i = n;
  int ans = 0;
  while (i >= 0) {
    if (i - 5 >= 0 && s.substr(i - 5, 5) == "CPCTF") {
      ans++;
      i -= 5;
      continue;
    }

    if (i - 7 >= 0 && s.substr(i - 7, 7) == "CPCTCPC") {
      ans++;
      i -= 7;
      continue;
    }

    i--;
  }
  cout << ans << endl;
}