n = int(input())
s = list(input() + '.......')
ans = 0
for i in range(n):
    if ''.join(s[i:i+5]) == 'CPCTF':
        ans += 1
    elif ''.join(s[i:i+7]) == 'CPCTCPC':
        ans += 1
        s[i+6] = '.'
print(ans)