N=int(input())
S=input()
idx=[]
for i in range(N):
    if S[i]=="T":
        if i<3 and S[i-3:i]!="CPC":
            continue
        if i+2<=N and S[i+1:i+2]=="F" or i+4<=N and S[i+1:i+4]=="CPC":
            idx.append(i)
le=len(idx)
use=[]
for i in idx:
    if use:
        p=use[-1]
        if S[p+1]=="C" and i-p<=6:
            continue
    use.append(i)
ans=len(use)
print(ans)