n = int(input())
s = input()

ans = 0
i = 0
while i < n:
    if i + 4 < n and s[i:i + 5] == "CPCTF":
        ans += 1
        i += 5
    elif i + 6 < n and s[i:i + 7] == "CPCTCPC":
        ans += 1
        i += 7
    else:
        i += 1
print(ans)