• Subtask 1(5 points): N <= 200
• Subtask 2(15 points): N <= 4, 000
• Subtask 3(80 points): N <= 200, 000

#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <string>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <queue>
#include <stack>
#include <iomanip>
#include <ios>
#include <cstdint>
#include <array>
#include <deque>
#include <numeric>

using namespace std;
 
#define MyFast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
#define int long long

constexpr long long N = 21;
constexpr long long MOD = 1e9 + 7;

void solve()
{
    int n;
    cin >> n;
    string s;
    cin >> s;

    vector <int> ans(n + 1);
    map <int, int> mp;

    int O = 0, I = 0, J = 0, fi = 0;

    for(int i = 0 ; i < n ; ++i)
    {
        if(s[i] == 'J')
        {
            J ++;
        }
        if(s[i] == 'I')
        {
            I ++;
        }
        if(s[i] == 'O')
        {
            O ++;
        }
        int temp = min(J, min(O, I));
        J -= temp;
        O -= temp;
        I -= temp;
        ans[i + 1] = temp + ans[i];

        if(mp[J + O * n + I * n * n])
        {
            fi = max(fi, ans[i + 1] - ans[mp[J + O * n + I * n * n]]);
        }
        else
        {
            mp[J + O * n + I * n * n] = i + 1;
        }
    }
    cout << 3 * fi << endl;
}

signed main()
{
    MyFast;
    int t = 1;
    //cin >> t;
        
    while (t--)
    {
        solve();
    }
}