n = int(input())
s = input()
i = 0
ans = 0
while i < n:
    if s[i:i+5] == 'CPCTF':
        ans += 1
        i += 5
    elif s[i:i+7] == 'CPCTCPC':
        ans += 1
        i += 7
    else:
        i += 1
print(ans)