#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define double long double
#define FOR(i, a, b) for(ll i = (a); i < (b); ++i)
#define FORR(i, a, b) for(ll i = (a); i > (b); --i)
#define REP(i, n) for(ll i = 0; i < (n); ++i)
#define REPR(i, n) for(ll i = n; i >= 0; i--)
#define FOREACH(x, a) for(auto &(x) : (a))
#define VECCIN(x)                                                              \
    for(auto &youso_ : (x)) cin >> youso_
#define bitcnt __builtin_popcount
#define SZ(x) ((ll)(x).size())
#define fi first
#define se second
#define All(a) (a).begin(), (a).end()
#define rAll(a) (a).rbegin(), (a).rend()

template <typename T = long long> inline T IN() {
    T x;
    cin >> x;
    return (x);
}
inline void CIN() {}
template <class Head, class... Tail>
inline void CIN(Head &&head, Tail &&... tail) {
    cin >> head;
    CIN(move(tail)...);
}
#define CCIN(...)                                                              \
    char __VA_ARGS__;                                                          \
    CIN(__VA_ARGS__)
#define DCIN(...)                                                              \
    double __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define LCIN(...)                                                              \
    ll __VA_ARGS__;                                                            \
    CIN(__VA_ARGS__)
#define SCIN(...)                                                              \
    string __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define Yes(a) cout << (a ? "Yes" : "No") << "\n"
#define YES(a) cout << (a ? "YES" : "NO") << "\n"
#define Printv(v)                                                              \
    {                                                                          \
        FOREACH(x, v) { cout << x << " "; }                                    \
        cout << "\n";                                                          \
    }
template <typename T = string> inline void eputs(T s) {
    cout << s << "\n";
    exit(0);
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
    std::fill((T *)array, (T *)(array + N), val);
}

template <typename T> using PQG = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using PQ = priority_queue<T>;

typedef long long ll;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<ll, ll> PL;
typedef vector<PL> VPL;
typedef vector<bool> VB;
typedef vector<double> VD;
typedef vector<string> VS;

const int INF = 1e9;
const int MOD = 1e9 + 7;
// const int MOD = 998244353;
const ll LINF = 5e18;
// const double PI = atan(1.0) * 4.0;
const ll dx[] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll dy[] = {0, 1, 1, 1, 0, -1, -1, -1};
#define PI 3.141592653589793238

// ローリングハッシュ
// 二分探索で LCP を求める機能つき
struct RollingHash {
    static const int base1 = 1007, base2 = 2009;
    static const int mod1 = 1000000007, mod2 = 1000000009;
    vector<long long> hash1, hash2, power1, power2;

    // construct
    RollingHash(const string &S) {
        int n = (int)S.size();
        hash1.assign(n + 1, 0);
        hash2.assign(n + 1, 0);
        power1.assign(n + 1, 1);
        power2.assign(n + 1, 1);
        for(int i = 0; i < n; ++i) {
            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;
        }
    }

    // get hash of S[left:right]
    inline pair<long long, long long> get(int l, int r) const {
        long long res1 = hash1[r] - hash1[l] * power1[r - l] % mod1;
        if(res1 < 0) res1 += mod1;
        long long res2 = hash2[r] - hash2[l] * power2[r - l] % mod2;
        if(res2 < 0) res2 += mod2;
        return {res1, res2};
    }

    // get lcp of S[a:] and T[b:]
    inline int getLCP(int a, int b) const {
        int len = min((int)hash1.size() - a, (int)hash1.size() - b);
        int low = 0, high = len;
        while(high - low > 1) {
            int mid = (low + high) >> 1;
            if(get(a, a + mid) != get(b, b + mid))
                high = mid;
            else
                low = mid;
        }
        return low;
    }
};

signed main() {
    LCIN(N);
    SCIN(S);

    RollingHash rh(S);

    auto check = [&](ll d) {
        map<PL, ll> memo;
        REP(i, N - d + 1) {
            auto x = rh.get(i, i + d);
            if (memo.count(x)) {
                if (i - memo[x] >= d) return true;
            }
            else memo[x] = i;
        }
        return false;
    };
    ll lb = 0, ub = N / 2 + 1;
    while(ub - lb > 1) {
        ll mid = (lb + ub) >> 1;
        if(check(mid))
            lb = mid;
        else
            ub = mid;
    }
    cout << lb << "\n";
}


Measured memory_bytes: 768