N = int(input())
S = input()
S += 'AAAAAAAAAAA'
ans = 0
i = 0
while i < N:
  s = S[i:i+4]
  if s == 'CPCT':
    if S[i+4:i+7] == 'CPC':
      i = i + 6
      ans += 1
    elif S[i+4] == 'F':
      ans += 1
      i = i + 4
  i += 1
  continue
print(ans)