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

cur = 0
l = 0
s1 = "CPCTF"
s2 = "CPCTCPC"
cnt = 0

mem = {}
def f(s):
    if len(s)<5:
        return 0
    a = [f(s[1:])]
    if s.startswith(s1):
        if s[len(s1):] not in mem:
            mem[s[len(s1):]] = f(s[len(s1):])
        a.append(mem[s[len(s1):]]+1)
    if s.startswith(s2):
        if s[len(s1):] not in mem:
            mem[s[len(s2):]] = f(s[len(s2):])
        a.append(mem[s[len(s2):]]+1)
    return max(a)
print(f(S)) 
"🐬?"