// #pragma GCC target "prefer-vector-width=512"
// #pragma GCC optimize "Ofast"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i,N) for(int i=0;i<(int)N;i++)
#define rrep(i,s,e) for(int i=s;i<(int)e;i++)
#define all(x) x.begin(),x.end()
#define vecin(N,A) rep(i,N) cin>>A[i]
#define vvecin(H,W,A) rep(i,H) rep(j,W) cin>>A[i][j]
string C = "CPCTF";
int main(){
    int N;cin>>N;
    string S;cin>>S;
    int ct = 0;
    int p = 0;
    rep(i,N){
        if(S[i]==C[p]){
            p++;
            if(p==5){
                p = 0;
                ct++;
            }
        }
        else if(p==4&&i+2<N&&S[i]=='C'&&S[i+1]=='P'&&S[i+2]=='C'){
            p = 0;
            ct++;
            i = i+2;
        }
        else {
            p=0;
        }
    }
    cout<<ct<<endl;
}