N = int(input())
S = input()

cur = 0
l = 0
s1 = "CPCTF"
s2 = "CPCTCPC"
cnt = 0
while True:
    if (l<=4 and S[cur]!=s1[l] and S[cur]!=s2[l]) or (l>4 and S[cur]!=s2[l]):
        l = 0
    elif l<=4 and S[cur]==s1[l]:
        l += 1
        if l == len(s1):
            cnt += 1
            l = 0
    elif S[cur]==s2[l]:
        l += 1
        if l==len(s2):
            cnt += 1
            l = 0
    cur += 1
    if cur==len(S):
        break
print(cnt)
"🐬"