n = int(input())
s = input().strip()

count_original = 0
for i in range(4, n):
    if s[i] == 'F' and s[i-4] == 'C' and s[i-3] == 'P' and s[i-2] == 'C' and s[i-1] == 'T':
        count_original += 1

candidates = []
for i in range(n - 2):
    if s[i] == 'C' and s[i+1] == 'P' and s[i+2] == 'C':
        if i >= 4 and s[i-4] == 'C' and s[i-3] == 'P' and s[i-2] == 'C' and s[i-1] == 'T':
            candidates.append(i)

count_replaced = 0
current_end = -1
for i in candidates:
    if i >= current_end:
        count_replaced += 1
        current_end = i + 3

print(count_original + count_replaced)