#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template<typename T> istream &operator>>(istream &is, vector<T> &vec){ for (auto &v : vec) is >> v; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec){ os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const deque<T> &vec){ os << "deq["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa){ os << "(" << pa.first << "," << pa.second << ")"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename T> void ndarray(vector<T> &vec, int len) { vec.resize(len); }
template<typename T, typename... Args> void ndarray(vector<T> &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) ndarray(v, args...); }
template<typename T> bool mmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template<typename T> bool mmin(T &m, const T q) { if (m > q) {m = q; return true;} else return false; }
template<typename T1, typename T2> pair<T1, T2> operator+(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first + r.first, l.second + r.second); }
template<typename T1, typename T2> pair<T1, T2> operator-(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first - r.first, l.second - r.second); }
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl;
#define FI first
#define SE second
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define POW2(n) (1LL << (n))

template<typename V>
struct rolling_hash
{
    V B;
    vector<V> hash; // hash[i] = s[0] * B^(i - 1) + ... + s[i - 1]
    vector<V> power; // power[i] = B^i
    rolling_hash() {}
    rolling_hash(const string &s, V b) : B(b)
    {
        int N = s.length();
        hash.resize(N + 1), power.resize(N + 1, 1);
        for (int i = 0; i < N; i++)
        {
            power[i + 1] = power[i] * B;
            hash[i + 1] = hash[i] * B + s[i];
        }
    }
    V get_hash(int l, int r) // s[l] * B^(r - l - 1) + ... + s[r - 1]
    {
        return hash[r] - hash[l] * power[r - l];
    }
};

using lint = long long;
using plint = pair<lint, lint>;
struct DoubleHash : public plint
{
    static plint MODs;
    DoubleHash(plint x) : plint(x) {}
    DoubleHash(lint x, lint y) : plint(x, y) {}
    DoubleHash(lint x) : DoubleHash(x, x) {}
    DoubleHash() : DoubleHash(0) {}
    static inline DoubleHash mod_subtract(plint x)
    {
        if (x.first >= MODs.first) x.first -= MODs.first;
        if (x.second >= MODs.second) x.second -= MODs.second;
        return x;
    }
    DoubleHash operator+(const DoubleHash &x) const
    {
        return mod_subtract(plint(this->first + x.first, this->second + x.second));
    }
    DoubleHash operator+(lint x) const
    {
        return mod_subtract(plint(this->first + x, this->second + x));
    }
    DoubleHash operator-(const DoubleHash &x) const
    {
        return mod_subtract(plint(this->first - x.first + MODs.first, this->second - x.second + MODs.second));
    }
    DoubleHash operator*(const DoubleHash &x) const
    {
        return make_pair(this->first * x.first % MODs.first, this->second * x.second % MODs.second);
    }
    DoubleHash operator*(lint x) const
    {
        return make_pair(this->first * x % MODs.first, this->second * x % MODs.second);
    }
};
plint DoubleHash::MODs = plint(1000000007, 998244353);

struct rand_int_
{
    using lint = long long;
    mt19937 mt;
    rand_int_() : mt(chrono::steady_clock::now().time_since_epoch().count()) {}
    lint operator()(lint x) { return this->operator()(0, x); } // [0, x)
    lint operator()(lint l, lint r) {
        uniform_int_distribution<lint> d(l, r - 1);
        return d(mt);
    }
} rnd;

int main()
{
    int N;
    cin >> N;
    string S;
    cin >> S;
    DoubleHash b(rnd(1, 1000000), rnd(1, 1000000));

    rolling_hash<DoubleHash> hash(S, b);

    IREP(ans, N / 2 + 1)
    {
        unordered_set<lint> s;
        REP(i, N)
        {
            if (i + ans <= N)
            {
                auto h = hash.get_hash(i, i + ans);
                if (s.count(h.first * 1e9 + h.second))
                {
                    cout << ans << endl;
                    return 0;
                }
            }
            if (i - ans + 1 >= 0)
            {
                auto h = hash.get_hash(i - ans + 1, i + 1);
                s.insert(h.first * 1e9 + h.second);
            }
        }
    }
    cout << 0 << endl;
}


Measured memory_bytes: 764