#include "bits/stdc++.h"
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
// https://codeforces.com/blog/entry/79148
class Timer: chrono::high_resolution_clock {
const time_point start_time;
public:
Timer(): start_time(now()) {}
rep elapsed_time() const {
return chrono::duration_cast<chrono::milliseconds>(now() - start_time).count();
}
} timer;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n;
string s;
cin >> n >> s;
s = "~" + s;
vector<ll> cntj(n + 2), cnto(n + 2), cnti(n + 2), cntjr(n + 2), cntor(n + 2), cntir(n + 2);
for (int i = 1; i <= n; i++) {
cntj[i] = cntj[i - 1];
cnto[i] = cnto[i - 1];
cnti[i] = cnti[i - 1];
if (s[i] == 'J') {
cntj[i]++;
}
if (s[i] == 'O') {
cnto[i] += cntj[i - 1];
}
if (s[i] == 'I') {
cnti[i] += cnto[i - 1];
}
}
for (int i = n; i >= 1; i--) {
cntjr[i] = cntjr[i + 1];
cntor[i] = cntor[i + 1];
cntir[i] = cntir[i + 1];
if (s[i] == 'J') {
cntjr[i] += cntor[i + 1];
}
if (s[i] == 'O') {
cntor[i] += cntir[i + 1];
}
if (s[i] == 'I') {
cntir[i]++;
}
}
ll ans = 0;
for (int i = 1; i <= n + 1; i++) {
ans = max({ans, cntor[i], cntj[i - 1] * cntir[i], cnto[i - 1]});
}
cout << ans + cnti[n];
return 0;
}
