from collections import deque

N = int(input())
S = deque(input())

def deque_slice(q, cnt):
    res = []
    for i in range(cnt):
        if i < len(q):
            res.append(q[i])
    return "".join(res)

s = []
ans = 0
while S:
    c = S.popleft()
    if c == "T":
        if "".join(s[-3:]) == "CPC":
            if deque_slice(S, 1) == "F":
                S.popleft()
                for _ in range(3):
                    s.pop()
                ans += 1
                continue
            elif deque_slice(S, 3) == "CPC":
                for _ in range(3):
                    S.popleft()
                    s.pop()
                ans += 1
                continue
    s.append(c)
print(ans)