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=len(arr)-1
while i>=0:
  if arr[i]=="CPC" or arr[i]=="F":
    if i-2>=0:
      if arr[i-1]=="T" and arr[i-2]=="CPC":
        i-=3
        ans+=1
        continue
  i+=1
print(ans)