#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <climits>
#include <cstring>

#define rep(i, m, n) for(int i=int(m);i<int(n);i++)
#define all(c) begin(c),end(c)

template<typename T1, typename T2>
inline void chmin(T1 &a, T2 b) { if (a > b) a = b; }

template<typename T1, typename T2>
inline void chmax(T1 &a, T2 b) { if (a < b) a = b; }

//改造
typedef long long int ll;
using ll = long long int;
using ull = long long unsigned int;
using Int = long long int;
using namespace std;
#define INF (1 << 30) - 1
#define INFl (ll)5e15
#define DEBUG 0 //デバッグする時1にしてね
#define dump(x)  cerr << #x << " = " << (x) << endl
#define MOD 1000000007


//ここから編集する
template<unsigned mod>
struct RollingHash {
    vector<unsigned> hashed, power;

    inline unsigned mul(unsigned a, unsigned b) const {
        unsigned long long x = (unsigned long long) a * b;
        unsigned xh = (unsigned) (x >> 32), xl = (unsigned) x, d, m;
        asm("divl %4; \n\t" : "=a" (d), "=d" (m) : "d" (xh), "a" (xl), "r" (mod));
        return m;
    }

    RollingHash(const string &s, unsigned base = 10007) {
        int sz = (int) s.size();
        hashed.assign(sz + 1, 0);
        power.assign(sz + 1, 0);
        power[0] = 1;
        for (int i = 0; i < sz; i++) {
            power[i + 1] = mul(power[i], base);
            hashed[i + 1] = mul(hashed[i], base) + s[i];
            if (hashed[i + 1] >= mod) hashed[i + 1] -= mod;
        }
    }

    unsigned get(int l, int r) const {
        unsigned ret = hashed[r] + mod - mul(hashed[l], power[r - l]);
        if (ret >= mod) ret -= mod;
        return ret;
    }

    unsigned connect(unsigned h1, int h2, int h2len) const {
        unsigned ret = mul(h1, power[h2len]) + h2;
        if (ret >= mod) ret -= mod;
        return ret;
    }

    int LCP(const RollingHash<mod> &b, int l1, int r1, int l2, int r2) {
        int len = min(r1 - l1, r2 - l2);
        int low = -1, high = len + 1;
        while (high - low > 1) {
            int mid = (low + high) / 2;
            if (get(l1, l1 + mid) == b.get(l2, l2 + mid)) low = mid;
            else high = mid;
        }
        return (low);
    }
};

using RH = RollingHash<1000000007>;

class Solve {
public:
    Int N;
    string S;


    void solve() {
        cin >> N >> S;
        RH rh = RH(S);

        auto check = [&](Int x) {
            map<Int, vector<Int>> mp;
            for (int i = 0; i + x <= S.size(); ++i) {
//                mp[rh.get(i, i + x)]++;
//                if (!mp.count(rh.get(i, i + x))) mp[rh.get(i, i + x)] = vector<Int>();
                mp[rh.get(i, i + x)].push_back(i);
            }
            for (auto e : mp) {
                if (e.second.size() >= 2) {
                    if (e.second.back() - e.second.front() >= x)
                        return true;
                }
            }
            return false;
        };

        Int ok = 0;
        Int ng = S.size() + 1;
        while (ng - ok > 1) {
            Int mid = (ok + ng) / 2;
            if (check(mid)) {
                ok = mid;
            } else {
                ng = mid;
            }
        }
        cout << ok << endl;


    }
};


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    Solve().solve();


    return 0;
}


Measured memory_bytes: 896