#line 2 "header.hpp"

//%snippet.set('header')%
//%snippet.fold()%
#ifndef HEADER_H
#define HEADER_H

// template version 2.0
using namespace std;
#include <bits/stdc++.h>

// varibable settings
const long long INF = 1e18;

#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (ll i = (ll)((b)-1); i >= (ll)(a); --i)
#define r_rep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define mt(...) make_tuple(__VA_ARGS__)
#define ub upper_bound
#define lb lower_bound
#define lpos(A, x) (lower_bound(all(A), x) - A.begin())
#define upos(A, x) (upper_bound(all(A), x) - A.begin())
template <class T>
inline void chmax(T &a, const T &b) {
    if ((a) < (b)) (a) = (b);
}
template <class T>
inline void chmin(T &a, const T &b) {
    if ((a) > (b)) (a) = (b);
}

#define divceil(a, b) ((a) + (b)-1) / (b)
#define is_in(x, a, b) ((a) <= (x) && (x) < (b))
#define uni(x)    \
    sort(all(x)); \
    x.erase(unique(all(x)), x.end())
#define slice(l, r) substr(l, r - l)

typedef long long ll;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef long double ld;
typedef pair<ll, ll> pii;
typedef tuple<ll, ll, ll> iii;

template <typename T>
using PQ = priority_queue<T, vector<T>, greater<T>>;
struct Fast {
    Fast() {
        std::cin.tie(0);
        ios::sync_with_stdio(false);
    }
} fast;
void check_input() {
    assert(cin.eof() == 0);
    int tmp;
    cin >> tmp;
    assert(cin.eof() == 1);
}

#if defined(PCM) || defined(LOCAL)
#else
#define dump(...) ;
#define dump_1d(...) ;
#define dump_2d(...) ;
#define cerrendl ;
#endif

#endif /* HEADER_H */
//%snippet.end()%
#line 2 "solve.cpp"

template <ll mod, ll B, class T = ll>
struct rolling_hash {
    vector<int> hash, _bpow;  // 1-index
    rolling_hash() {}
    rolling_hash(vector<T> vs) { init(vs); }
    rolling_hash(string &s) {
        vector<T> vs;
        for (char c : s) vs.emplace_back(c);
        init(vs);
    }

    void init(vector<T> vs) {
        int n = vs.size();
        hash.assign(n + 1, 0);
        _bpow.assign(n + 1, 1);
        for (int i = 0; i < n; i++) {
            hash[i + 1] = ((ll)hash[i] * B + vs[i]) % mod;
            _bpow[i + 1] = (ll)_bpow[i] * B % mod;
        }
    }

    // S[l, r)
    int get_hash(int l, int r) {
        int res = hash[r] + mod - (ll)hash[l] * _bpow[r - l] % mod;
        return res >= mod ? res - mod : res;
    }
};
using RH = rolling_hash<1000000009, 10009>;

int solve() {
    int n;cin>>n;
    string s;cin>>s;

    RH rh(s);
    int left = 0;
    int right = 1000000;

    auto is_right = [&](int k){
        unordered_map<int, int> d;
        for(int i=0; i+k-1<n; i++){
            int h = rh.get_hash(i, i+k);
            dump(k, d, h, i);
            if (d.find(h)==d.end()){
                d[h] = i+k;
            }
            else{
                dump(k);
                if (d[h]<=i) return false;
            }
        }
        return true;
    };
    while(right-left>1){
        int m = (right+left)/2;
        dump(m);
        if (is_right(m)) right = m;
        else             left  = m;
    }
    cout << right-1 << endl;

    return 0; 
}


int main(){/*{{{*/
    solve();
    check_input();
    return 0;
}/*}}}*/


Measured memory_bytes: 640