N=int(input())
S=input()
queue=[]
for s in S:
    queue.append(s)
    if len(queue)>=4 and queue[-4:]==list("TCPC"):
        for _ in range(3):
            queue.pop()
        queue.append("F")
ans=0
N=len(queue)
for i in range(N-4):
    if queue[i:i+5]==list("CPCTF"):
        ans+=1
print(ans)