#include <bits/stdc++.h>
using namespace std;
template <class T>
bool chmin(T& _old, T _new) { return _old > _new && (_old = _new, true); }
template <class T>
bool chmax(T& _old, T _new) { return _old < _new && (_old = _new, true); }
int main() {
cin.tie(nullptr)->sync_with_stdio(false);
#ifdef palilo
freopen("in", "r", stdin);
freopen("out", "w", stdout);
#endif
int n;
string s;
cin >> n >> s;
int64_t ans = 0, cur = 0;
{
// case 'I'
int64_t j = 0, o = 0;
for (const auto& c : s) {
if (c == 'J') {
++j;
} else if (c == 'O') {
o += j;
} else {
cur += o;
}
}
ans = cur + o;
}
{
// case 'J'
int64_t j = 1, o = 0, res = 0;
for (const auto& c : s) {
if (c == 'J') {
++j;
} else if (c == 'O') {
o += j;
} else {
res += o;
}
}
chmax(ans, res);
}
{
// case 'O'
int64_t j = 0, i = count(s.begin(), s.end(), 'I');
for (const auto& c : s) {
if (c == 'J') {
++j;
} else if (c == 'I') {
--i;
}
chmax(ans, cur + j * i);
}
}
cout << ans;
}
