N=int(input())
S=input()
ans=0
i=0
while i<len(S):
  if i+6<len(S):
    if S[i:i+7]=="CPCTCPC":
      ans+=1
      i+=7
      continue
  if i+4<len(S):
    if S[i:i+5]=="CPCTF":
      ans+=1
      i+=5
      continue
  i+=1
print(ans)