#include <bits/stdc++.h>
using namespace std;
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n;
    string s;
    cin >> n >> s;
    vector<int> cnt(3);
    vector<array<int, 3>> nx(n + 1);
    nx[n][0] = nx[n][1] = nx[n][2] = n;
    for (int i = n - 1; ~i; --i) {
        ++cnt[s[i] - 'a'];
        nx[i] = nx[i + 1];
        nx[i][s[i] - 'a'] = i;
    }
    int ans = 0;
    for (int i = 0; i < 3; ++i) ans = max(ans, cnt[i] * cnt[i]);
    for (int i = 2, pw3 = 9; n * (n / i) > ans; ++i, pw3 *= 3) {
        vector<int> b(i);
        for (int s = 0; s < pw3; ++s) {
            for (int j = 0, tmp = s; j < i; ++j, tmp /= 3) {
                b[j] = tmp % 3;
            }
            int len = 0;
            for (int ps = -1; ps < n; ) {
                ps = nx[ps + 1][b[len % i]];
                ++len; 
            }
            // if (i == 2) {
            //     for (int j = 0; j < i; ++j) cout << char('a' + b[j]);
            //     cout << " " << len << endl;
            // }
            len = (len - 1) / i * i;
            ans = max(ans, len * len / i);
        }
    }
    cout << ans << endl;
    return 0;
}