#include<bits/stdc++.h>

using namespace std;

int n;
string s;
int pt;
int cp(){
  if(s[pt]=='C' && s[pt+1]=='P' && s[pt+2]=='C'  && s[pt+3]=='T'){
    if(s[pt+4]=='F'){return 5;}
    if(s[pt+4]=='C' && s[pt+5]=='P' && s[pt+6]=='C'){return 7;}
  }
  return 1;
}

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  cin >> n;
  cin >> s;
  for(int i=0;i<100;i++){s.push_back('.');}

  int res=0;
  pt=0;
  while(pt<n){
    int d=cp();
    if(d>1){res++;}
    pt+=d;
  }
  cout << res << "\n";
  return 0;
}