N=int(input())
S=input().strip()

ANS=0
ind=len(S)-1

while ind>=0:
    if ind-4>=0 and S[ind-4:ind+1]=="CPCTF":
        ANS+=1
        ind-=5
    elif ind-6>=0 and S[ind-6:ind+1]=="CPCTCPC":
        ANS+=1
        ind-=7
    else:
        ind-=1

print(ANS)