def count_cpctf(n, s):
    count_cpctf = 0

    for i in range(n - 4):
        if s[i:i+3] == "CPC":
            if s[i+3:i+5] == "TF":
                count_cpctf += 1
                i += 5
            elif s[i+3:i+7] == "TCPC":
                count_cpctf += 1
                i += 7
            else:
                i += 1
        else:
            i += 1 
            
    return count_cpctf

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

result = count_cpctf(n, s)
print(result)