#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using VI = vector<int>;
using VL = vector<ll>;
template<class T> using PQ = priority_queue<T, vector<T>, greater<T>>;
#define FOR(i,a,n) for(int (i)=(a);(i)<(n);++(i))
#define eFOR(i,a,n) for(int (i)=(a);(i)<=(n);++(i))
#define rFOR(i,a,n) for(int (i)=(n)-1;(i)>=(a);--(i))
#define erFOR(i,a,n) for(int (i)=(n);(i)>=(a);--(i))
#define each(i, a) for(auto &i : a)
#define SORT(i) sort((i).begin(),(i).end())
#define rSORT(i,a) sort((i).begin(),(i).end(),(a))
#define all(i) (i).begin(),(i).end()
#define out(y,x) ((y) < 0 || h <= (y) || (x) < 0 || w <= (x))
#define line cout << "------------------------\n" 
#define ENDL(i,n) ((i) == (n) - 1 ? "\n" : " ")
#define stop system("pause") //comment out this on AOJ.
constexpr ll INF = 1000000000;
constexpr ll LLINF = 1LL << 60;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr ld eps = 1e-10; //1e-9?
constexpr ld pi = 3.1415926535897932;
template<class T>inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T>inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; }return false; }
inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); }
template<class T>inline istream& operator>>(istream& is, vector<T>& v) { for (auto& elemnt : v)is >> elemnt; return is; }
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template<class T>inline vector<T> vec(size_t a) { return vector<T>(a); }
template<class T>inline vector<T> defvec(T def, size_t a) { return vector<T>(a, def); }
template<class T, class... Ts>inline auto vec(size_t a, Ts... ts) { return vector<decltype(vec<T>(ts...))>(a, vec<T>(ts...)); }
template<class T, class... Ts>inline auto defvec(T def, size_t a, Ts... ts) { return vector<decltype(defvec<T>(def, ts...))>(a, defvec<T>(def, ts...)); }

struct RollingHash {
    ll base1 = 1007, base2 = 2009;
    ll mod1 = mod, mod2 = MOD;
    VL hash1, hash2, power1, power2;

    RollingHash(const string& S) {
        int n = S.size();
        hash1.assign(n + 1, 0);
        hash2.assign(n + 1, 0);
        power1.assign(n + 1, 1);
        power2.assign(n + 1, 1);
        FOR(i, 0, n) {
            hash1[i + 1] = (hash1[i] * base1 + S[i]) % mod1;
            hash2[i + 1] = (hash2[i] * base2 + S[i]) % mod2;
            power1[i + 1] = (power1[i] * base1) % mod1;
            power2[i + 1] = (power2[i] * base2) % mod2;
        }
    }

    inline pair<ll, ll> hash(int l, int r) const {
        ll res1 = hash1[r] - hash1[l] * power1[r - l] % mod1;
        if (res1 < 0) res1 += mod1;
        ll res2 = hash2[r] - hash2[l] * power2[r - l] % mod2;
        if (res2 < 0) res2 += mod2;
        return { res1, res2 };
    }
};

int main() {
    init();

    int n; cin >> n;
    string s; cin >> s;

    RollingHash rh(s);
    function<bool(int)> check = [&](int x) {
        map<pair<ll, ll>, int> m;
        eFOR(i, 0, n - x) {
            auto hash = rh.hash(i, i + x);
            if (m.count(hash)) {
                if (x <= i - m[hash])return true;
            }
            else m[hash] = i;
        }
        return false;
    };

    int ok = 0, ng = n;
    while (ng - ok > 1) {
        int mid = (ok + ng) / 2;
        if (check(mid))ok = mid;
        else ng = mid;
    }
    cout << ok << "\n";
}

Measured memory_bytes: 768