#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
ll pre[100005][3];
ll suf[100005][3];
int main(){
ios_base::sync_with_stdio(false), cin.tie(0);
cout.precision(10);
cout << fixed;
int n;
cin >> n;
string s;
cin >> s;
for(int i=1; i<=n; i++){
pre[i][0] = pre[i-1][0];
pre[i][1] = pre[i-1][1];
pre[i][2] = pre[i-1][2];
if(s[i-1] == 'J'){
pre[i][0]++;
}
else if(s[i-1] == 'O'){
pre[i][1] += pre[i][0];
}
else{
pre[i][2] += pre[i][1];
}
}
for(int i=n; i>=1; i--){
suf[i][0] = suf[i+1][0];
suf[i][1] = suf[i+1][1];
suf[i][2] = suf[i+1][2];
if(s[i-1] == 'I'){
suf[i][0]++;
}
else if(s[i-1] == 'O'){
suf[i][1] += suf[i][0];
}
else{
suf[i][2] += suf[i][1];
}
}
ll res = 0;
for(int i=0; i<=n; i++){
res = max(res, suf[i+1][1]);
res = max(res, pre[i][1]);
res = max(res, pre[i][0]*suf[i+1][0]);
}
cout << res + pre[n][2] << "\n";
return 0;
}
