#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define X first
#define Y second
#define pb push_back
#define ALL(v) v.begin(), v.end()
#define SZ(a) ((int)a.size())

const int N = 1e4 + 5;
int nxt[N][3];
int n;
int ans;
int p[15];

int chk(int L) {
    int cur = -1;
    int tt = 0;
    while (cur < n) {
        for (int i = 0; cur < n && i < L; i++)
            cur = nxt[cur + 1][p[i]];
        if (cur < n)
            tt += L;      
    }
    // if (L <= 3)
    //     cerr << L << " " << tt << endl;
    return tt;
}

void dfs(int lv) {
    if (lv == 8)
        return;
    for (int i = 0; i < 3; i++) {
        p[lv] = i;
        int r = chk(lv + 1);
        ans = max(ans, r * r / (lv + 1));
        dfs(lv + 1);
    }
}


int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    cin >> n;
    string s;
    cin >> s;
    for (int i = 0; i < 3; i++)
        nxt[n][i] = n;
    for (int i = n - 1; i >= 0; i--)
        for (int j = 0; j < 3; j++)
            nxt[i][j] = (s[i] - 'a' == j ? i : nxt[i + 1][j]);
    dfs(0);
    cout << ans << endl;
}