def solve(n,S):
    res=0
    i=3
    while i<n-1:
        if S[i]!='T':
            i+=1
            continue
        if S[i-3:i]!="CPC":
            i+=4
            continue
        if S[i+1:i+4]=="CPC":
            res+=1
            i+=5
        elif S[i+1]=='F':
            res+=1
            i+=2
        else:
            i+=4
    return res

print(solve(int(input()),input()))