from collections import deque
N=int(input())
S=input()
arr=[]
i=0
while i<len(S):
  if i+2<len(S):
    if S[i]+S[i+1]+S[i+2]=="CPC":
      arr.append("CPC")
      i+=3
      continue
  arr.append(S[i])
  i+=1
ans=0
i=0
while i<len(arr):
  if arr[i]=="CPC":
    if i+2<len(arr):
      if arr[i+1]=="T" and (arr[i+2]=="F" or arr[i+2]=="CPC"):
        i+=3
        ans+=1
        continue
  i+=1
print(ans)