N=int(input())
S=" "+input()
T=[" " for _ in range(N+1)]
N+=1
for i in range(N-3+1):
    if S[i:i+3]=="CPC":
        T[i]="F";T[i+1]=" ";T[i+2]=" "
T="".join(T)
dp=[[0,0] for _ in range(N+1)]
i=5
while i<=N:
    if S[i-4:i]=="CPCT":
        if S[i]=="F":
            dp[i][0]=max(dp[i-1][0]+1,dp[i-1][1]+1)
            dp[i][1]=dp[i-1][1]
        if T[i]=="F":
            dp[i][0]=dp[i-1][0]
            dp[i][1]=max(dp[i-1][0]+1,dp[i-1][1]+1)
            for _ in range(2):
                i+=1
                dp[i][0]=dp[i-1][0]
                dp[i][1]=dp[i-1][1]
    else:
        dp[i][0]=dp[i-1][0]
        dp[i][1]=dp[i-1][1]
    i+=1
print(max(dp[N]))