N = int(input())
S = input()
Sl = S.split('T')
ans = 0
for i in range(1, len(Sl)):
    if len(Sl[i-1]) >= 3 and Sl[i-1][-3:] == "CPC":
        if len(Sl[i]) >= 1 and Sl[i][0] == "F":
            ans += 1
        elif len(Sl[i]) >= 3 and Sl[i][:3] == "CPC":
            ans += 1
            Sl[i] = Sl[i][3:]
print(ans)