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

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