#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template <class T> using treap = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define int long long
#define REP(i, n) for (long long i = 0, max_i = (n); i < max_i; i++)
#define REPI(i, a, b) for (long long i = (a), max_i = (b); i < max_i; i++)
#define ALL(obj) begin(obj), end(obj)
#define RALL(obj) rbegin(obj), rend(obj)
#define fi first
#define se second
using ii = pair<int, int>;
vector<ii> dirs = {
    {1, 0}, {0, 1}, {-1, 0}, {0, -1},  // 4方向
    {1, 1}, {-1, 1}, {-1, -1}, {1, -1},  // 斜め
    {0, 0},  // 自身
};
template <class T> inline bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } return false; }
template <class T> inline bool chmin(T& a, const T& b) { if (a > b) { a = b; return true; } return false; }
template <class T, class S> vector<T> make_vec(size_t n, S x) { return vector<T>(n, x); }
template <class T, class... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec<T>(ts...))>(n, make_vec<T>(ts...)); }

// debug
template <class T> ostream& operator<<(ostream& s, vector<T>& d) { REP (i, d.size()) s << d[i] << (i == d.size() - 1 ? "" : " "); return s; }
template <class T> ostream& operator<<(ostream& s, vector<vector<T>>& d) { REP (i, d.size()) s << d[i] << (i == d.size() - 1 ? "" : "\n"); return s; }
template <class T, class S> ostream& operator<<(ostream& s, pair<T, S>& p) { s << "{" << p.first << ", " << p.second << "}"; return s; }
template <class T> ostream& operator<<(ostream& s, set<T> m) { for (auto it = m.begin(); it != m.end(); it++) { s << *it << (next(it) == m.end() ? "" : "\n"); } return s; }
template <class T> ostream& operator<<(ostream& s, multiset<T> m) { for (auto it = m.begin(); it != m.end(); it++) { s << *it << (next(it) == m.end() ? "" : "\n"); } return s; }
template <class T, class S> ostream& operator<<(ostream& s, map<T, S> m) { for (auto it = m.begin(); it != m.end(); it++) { s << *it << (next(it) == m.end() ? "" : "\n"); } return s; }
template <class T, class S> ostream& operator<<(ostream& s, unordered_map<T, S> m) { for (auto it = m.begin(); it != m.end(); it++) { s << *it << (next(it) == m.end() ? "" : "\n"); } return s; }
#ifdef _MY_DEBUG
    #define dump(...) cerr << "/* " << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]" << endl, dump_func(__VA_ARGS__), cerr << "*/\n\n";
#else
    #define dump(...)
    #define endl "\n"
#endif
void dump_func() { cerr << endl; }
template <class Head, class... Tail> void dump_func(Head&& h, Tail&&... t) { cerr << h << (sizeof...(Tail) == 0 ? "" : ", "), dump_func(forward<Tail>(t)...); }

struct Fast { Fast() { cin.tie(nullptr); ios::sync_with_stdio(false); } } fast;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
constexpr int MOD = 1000000007;
// *************** TEMPLATE END *************** 

using ull = unsigned long long;
struct RollingHash {
    vector<ull> hash, pows;
    ull base, mod;
    RollingHash(const string &S, ull base, ull mod = 1000000009)
        : hash(S.size() + 1), pows(S.size() + 1, 1), mod(mod), base(base) {
        for (int i = 0; i < S.size(); i++) {
            pows[i + 1] = pows[i] * base % mod;
            hash[i + 1] = hash[i] * base % mod + S[i];
            if (hash[i + 1] >= mod) hash[i + 1] -= mod;
        }
    }
    // [l, r)
    ull get(int l, int r) {
        dump(l, r);
        assert(l <= r);
        ull ret = hash[r] + mod - hash[l] * pows[r - l] % mod;
        if (ret >= mod) ret -= mod;
        return ret;
    }
    void concat(const string &T) {
        int n = hash.size() - 1, m = T.size();
        pows.resize(n + m + 1);
        hash.resize(n + m + 1);
        for (int i = 0; i < m; i++) {
            pows[n + i + 1] = pows[n + i] * base % mod;
            hash[n + i + 1] = hash[n + i] * base % mod + T[i];
            if (hash[n + i + 1] >= mod) hash[n + i + 1] -= mod;
        }
    }
};

constexpr int HASH_NUM = 1;
struct bases_t {
    int use[HASH_NUM];
    int &operator[](int i) { return use[i]; }
    bases_t() {
        mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
        for (int i = 0; i < HASH_NUM; i++) use[i] = rnd() % 1000000;
    }
} bases;

using multihash_t = array<int, HASH_NUM>;
struct MultiRollingHash {
    vector<RollingHash> rhs;
    MultiRollingHash(const string &S) {
        for (int i = 0; i < HASH_NUM; i++) {
            rhs.push_back(RollingHash(S, bases[i]));
        }
    }
    multihash_t get(int l, int r) {
        multihash_t ret;
        for (int i = 0; i < HASH_NUM; i++) ret[i] = rhs[i].get(l, r);
        return ret;
    }
    void concat(const string &T) {
        for (int i = 0; i < HASH_NUM; i++) rhs[i].concat(T);
    }
};

signed main() {
    int n; cin >> n;
    string s; cin >> s;
    MultiRollingHash rh(s);
    auto check = [&](int len) -> bool {
        REP (i, n - len + 1) {
            auto hash1 = rh.get(i, i + len);
            REPI (j, i + len, n - len + 1) {
                if (hash1 == rh.get(j, j + len)) return true;
            }
        }
        return false;
    };
    int ok = 0, ng = n;
    while (abs(ok - ng) > 1) {
        int m = (ok + ng) / 2;
        (check(m) ? ok : ng) = m;
    }
    cout << ok << endl;
}


Measured memory_bytes: 384