#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <array>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <stack>
#include <queue>
#include <bitset>
#include <tuple>
#include <cmath>
#include <complex>
#include <algorithm>
#include <utility>
#include <regex>
#include <cstdint>
#include <numeric>
#include <functional>
#include <cassert>

using namespace std;
using ll = long long;
using ull = unsigned long long;

constexpr ll INF = 1'000'000'000'000'000'000;
namespace utils{
#define ALL(x) begin(x), end(x)
#define RALL(x) rbegin(x), rend(x)
    template<class T, class Compare> using p_queue = priority_queue<T, vector<T>, Compare>;
    template<class T> using min_queue = p_queue<T, greater<T>>;
    template<class T> using max_queue = p_queue<T, less<T>>;

    template<class T> bool up_min(T& X, const T& A){ if(X > A) {X = A; return true;} return false; }
    template<class T> bool up_max(T& X, const T& A){ if(X < A) {X = A; return true;} return false; }

    ll operator"" _64(unsigned long long x){ return ll(x); }
    ull operator"" _64u(unsigned long long x){ return ull(x); }

    template<class T>
    vector<T> make_mdvector(int n, T t){
        return vector<T>(n, t);
    }
    template<class ...Ts>
    auto make_mdvector(int n, Ts ... ts){
        return vector<decltype(make_mdvector(ts...))>(n, make_mdvector(ts...));
    }

    inline ll bit(int x){
        return 1ll << x;
    }

    template<class T>
    istream& operator>>(istream& is, vector<T>& v){
        for (auto &&x : v) { is >> x; } return is;
    }

    template<class T>
    ostream& operator<<(ostream& os, const vector<T>& v){
        for (auto &&x : v) { os << x << ' '; } cout << endl; return os ;
    }
}
using namespace utils;

class RollingHash {
    vector<vector<ull>> hashed, power;
    string S;
    const vector<ull> bases = {1'234'567, 67'280'421'310'721};
    static constexpr ull MOD = (1ul << 61ul) - 1;

    static inline ull mul(ull a, ull b) {
        constexpr ull mask_30 = (1ull << 30ull) - 1;
        constexpr ull mask_31 = (1ull << 31ull) - 1;
        ull a_u = a >> 31ull;
        ull b_u = b >> 31ull;
        ull a_d = a & mask_31;
        ull b_d = b & mask_31;

        ull mid = a_d * b_u + a_u * b_d;
        ull mid_u = mid >> 30ull;
        ull mid_d = mid & mask_30;

        return calc_mod(a_u * b_u * 2ull + mid_u + (mid_d << 31ull) + a_d * b_d);
    }

    static inline ull calc_mod(ull val) {
        val = (val & MOD) + (val >> 61ull);
        if(val >= MOD) val -= MOD;
        return val;
    }

public:
    RollingHash() = default;
    explicit RollingHash(const string& s) {
        init(S);
    }

    void init(const string& s){
        S = s;
        auto N = S.size();
        hashed.resize(2);
        power.resize(2);
        for (int k = 0; k < 2; ++k) {
            auto &&hash = hashed[k];
            auto &&pow = power[k];
            auto &&base = bases[k];
            hash.resize(N + 1);
            hash[0] = 0;
            pow.resize(N + 1);
            pow[0] = 1;
            for (int i = 0; i < N; ++i) {
                hash[i + 1] = calc_mod(mul(hash[i], base) + S[i]);
                pow[i + 1] = calc_mod(mul(pow[i], base));
            } // end i
        }
    }

    // get hash(t) : S[l, r)
    inline ull get(int l, int r, int t) const {
        ull ret = hashed[t][r] + MOD - mul(hashed[t][l], power[t][r-l]);
        ret = calc_mod(ret);
        return ret;
    }

    inline pair<ull, ull> get(int l, int r) const {
        return {get(l, r, 0), get(l, r, 1)};
    }
};

class solver{
    istream& is;
    ostream& os;

public:
    solver(istream& I, ostream& O) :is(I), os(O) {}
    ll N;
    string S;
    RollingHash rhs;
    void run();

    bool check(int m){
        for (int i = 0; i < N; ++i) {
            auto Si = rhs.get(i, i+m);
            for (int j = i + m; j < N; ++j) {
                if(j+m > N) break;
                if(Si == rhs.get(j, j+m)) return true;
            } // end j
        } // end i
        return false;
    }
};

int main(int argc, char *argv[]) {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << setprecision(16) << scientific;
#ifdef XELMH
    string test_cases = "test_E.txt";
    cerr << test_cases << " -->" << endl;
    auto fs = fstream(test_cases, fstream::in);
    int loop = 0;
    while(fs) {
        loop++;
        cout << '#' << loop << "#------\n";
        solver(fs, cout).run();
    }
    if(loop <= 1) {
        cout << "===" << endl;
        while(cin) solver(cin, cout).run();
    }
#else
    solver(cin, cout).run();
#endif
    return 0;
}


void solver::run(){
    is >> N >> S;
    if(!is) return;
    rhs.init(S);
    int NG = N, OK = 0;
    while(NG - OK > 1){
        int mid = (OK + NG) / 2;
        if(check(mid)) OK = mid;
        else NG = mid;
    }
    os << OK << endl;
}


Measured memory_bytes: 384