import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

n = ni()
s = input()
s = list(s)
#print(s)
ans = 0
i = 0
while i < n-4:
    if s[i: i+5] == list("CPCTF"):
        ans += 1
        i += 5
    elif s[i: i+7] == list("CPCTCPC"):
        i += 7
        ans += 1
    else:
        i += 1

print(ans)