/* -*- coding: utf-8 -*-
 *
 * 2738.cc:  No.2738 CPC To F - yukicoder
 */

#include<cstdio>
#include<cstring>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 500000;
const char cpct[] = "CPCT";
const char cpc[] = "CPC";

/* typedef */

/* global variables */

char s[MAX_N + 4];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d%s", &n, s);

  int cnt = 0;
  for (int i = 0; i < n;) {
    if (i + 4 <= n && strncmp(s + i, cpct, 4) == 0) {
      i += 4;
      if (i + 1 <= n && s[i] == 'F') cnt++, i++;
      else if (i + 3 <= n && strncmp(s + i, cpc, 3) == 0) {
	cnt++;
	s[i++] = 'F', s[i++] = '-', s[i++] = '-';
      }
    }
    else
      i++;
  }

  printf("%d\n", cnt);
  
  return 0;
}