#include <bits/stdc++.h> using namespace std; map<pair<int, int>, int> mp; int32_t main() { ios::sync_with_stdio(0); cin.tie(0); int n, ans = 0; string s; cin >> n >> s; vector<int> cnt(3, 0); map<char, int> cv = {{'J', 0}, {'O', 1}, {'I', 2}}; mp[{0, 0}] = -1; for (int i = 0; i < n; i++) { cnt[cv[s[i]]]++; pair<int, int> tmp = {cnt[1] - cnt[0], cnt[2] - cnt[1]}; if (!mp.count(tmp)) mp[tmp] = i; else ans = max(ans, i - mp[tmp]); } cout << ans << '\n'; return 0; }