#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;

#define REP(i,n) for(long long i = 0; i < (n); i++)
#define FOR(i, m, n) for(long long i = (m);i < (n); ++i)
#define ALL(obj) (obj).begin(),(obj).end()
#define SPEED cin.tie(0);ios::sync_with_stdio(false);

template<class T> using V = vector<T>;
template<class T, class U> using P = pair<T, U>;

const ll MOD = (ll)1e9 + 7;
const ll MOD2 = 998244353;
const ll HIGHINF = (ll)1e18;
const ll LOWINF = (ll)1e15;
const long double PI = 3.1415926535897932384626433;

template <class T> void corner(bool flg, T hoge) {if (flg) {cout << hoge << endl; exit(0);}}
template <class T, class U>ostream &operator<<(ostream &o, const map<T, U>&obj) {o << "{"; for (auto &x : obj) o << " {" << x.first << " : " << x.second << "}" << ","; o << " }"; return o;}
template <class T>ostream &operator<<(ostream &o, const set<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const multiset<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const vector<T>&obj) {o << "{"; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "}"; return o;}
template <class T, class U>ostream &operator<<(ostream &o, const pair<T, U>&obj) {o << "{" << obj.first << ", " << obj.second << "}"; return o;}
template <template <class tmp>  class T, class U> ostream &operator<<(ostream &o, const T<U> &obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr)o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
void print(void) {cout << endl;}
template <class Head> void print(Head&& head) {cout << head;print();}
template <class Head, class... Tail> void print(Head&& head, Tail&&... tail) {cout << head << " ";print(forward<Tail>(tail)...);}
template <class T> void chmax(T& a, const T b){a=max<T>(a,b);}
template <class T> void chmin(T& a, const T b){a=min<T>(a,b);}
void YN(bool flg) {cout << ((flg) ? "YES" : "NO") << endl;}
void Yn(bool flg) {cout << ((flg) ? "Yes" : "No") << endl;}
void yn(bool flg) {cout << ((flg) ? "yes" : "no") << endl;}

int main() {
    int N; cin >> N;
    string S,W; cin >> S;
    W.push_back(S[0]);
    for(int i = 1; i < S.size(); ++i){
        W.push_back('.');
        W.push_back(S[i]);
    }

    N = W.size();

    V<ll> L(N,0),R(N,0);

    for(int i = 0; i < N-1; ++i){
        if(W[i] == 'J') L[i+1]++;
        L[i+1] += L[i];
    }
    for(int i = N-1; 0 < i; --i){
        if(W[i] == 'I') R[i-1]++;
        R[i-1] += R[i];
    }

    string T = "J" + S, U = S + "I";
    ll J,JO,JOI,ans = 0;
    J = JO = JOI = 0;
    for(int i = 0; i < T.size(); ++i){
        if(T[i]=='J') J += 1;
        if(T[i]=='O') JO += J;
        if(T[i]=='I') JOI += JO;
    }
    chmax(ans,JOI);

    J = JO = JOI = 0;
    for(int i = 0; i < U.size(); ++i){
        if(U[i]=='J') J += 1;
        if(U[i]=='O') JO += J;
        if(U[i]=='I') JOI += JO;
    }
    chmax(ans,JOI);

    ll sum = 0;
    for(int i = 0; i < N; ++i) if(W[i]=='O') sum += L[i]*R[i];
    chmax(ans,sum);
    for(int i = 0; i < N; ++i) if(W[i]=='.') chmax(ans,sum+L[i]*R[i]);
    cout << ans << endl;

	return 0;
}



Measured memory_bytes: 6748