#include <bits/stdc++.h>
#define pb push_back
#define F first
#define S second
#define all(v) v.begin(),v.end()
#define Gondozu ios::sync_with_stdio(false);cout.tie(NULL);cin.tie(NULL);

using namespace std;
using ll = long long;
using pi = pair<int, int>;
using vi = vector<int>;
using vpi = vector <pair<int, int>>;
using vvi = vector <vector<int>>;

const int OO = 1e9 + 5;
const int N = 2e5 + 5;

string cur, s;
int n, ans;
void gen(int i){
    // eval cur

    if(i != 0){
        int idx = 0, len = 0;
        for (int j = 0; j < n; ++j) {
            if(s[j] == cur[idx]){
                (++idx) %= i;
                if(idx==0) len += i;
            }
        }
        ans = max(ans, len * len / i);
    }

    if(i == min(8,n))
        return;
    for (char c = 'a'; c <= 'c'; ++c) {
        cur.pb(c);
        gen(i+1);
        cur.pop_back();
    }
}

void TC()
{
    cin >> n >> s;
    ans = ((n+2)/3) * ((n+2)/3);
    gen(0);
    cout << ans;
}

int32_t main() {
    Gondozu
    int t = 1;
//    cin >> t;
    while (t--) {
        TC();
        cout << '\n';
    }
    return 0;
}