#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
inline void fastio() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
}
ll n;
string s;
int main() {
fastio();
cin >> n >> s;
vector<ll> js(n + 1), is(n + 1);
for (ll i = 0; i < n; i++) {
js[i + 1] = js[i] + (s[i] == 'J');
is[i + 1] = is[i] + (s[i] == 'I');
}
ll jt = 0, it = 0, ot = 0, ans = 0;
for (ll i = 1; i < n; i++) {
ot = max(ot, js[i] * (is[n] - is[i]));
}
for (ll i = 0; i < n; i++) if (s[i] == 'O') {
jt += is[n] - is[i + 1];
it += js[i];
ans += js[i] * (is[n] - is[i + 1]);
}
ans += max({ot, jt, it});
cout << ans;
return 0;
}
