//#include <bits/stdc++.h>

#include <iostream>
#include <algorithm>

#include <bitset>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <stack>
#include <queue>
#include <deque>
#include <cstring>
#include <string>
#include <utility>
#include <array>
#include <complex>
#include <valarray>

#include <cassert>
#include <cmath>
#include <functional>
#include <iomanip>
#include <chrono>
#include <random>
#include <numeric>

#include<memory>


using namespace std;
//#define int long long

typedef long long ll;
typedef unsigned long long ull;
//typedef unsigned __int128 HASH;
typedef pair<int,int> pii;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pullull;
typedef pair<ll,int> plli;
typedef pair<double,int> pdi;
typedef pair<long double, int> pdbi;
typedef pair<int,pii> pipii;
typedef pair<ll,pll> plpll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<pii> vpii;
typedef vector<vector<int>> mat;

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n);i>0;i--)
#define rrep2(i,a,b) for (int i=(a);i>b;i--)
#define pb push_back
#define fi first
#define se second
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()

const ll hmod1 = 999999937;
const ll hmod2 = 1000000000 + 9;
const int INF = 1<<30;
const ll INFLL = 1LL<<62;
const long double EPS = 1e-12;
const ll mod = 1000000000 + 7;
//const ll mod = 998244353;
const int dx4[4] = {1, 0, -1, 0};
const int dy4[4] = {0, 1, 0, -1};
const int dx8[8] = {1, 1, 1, 0, 0, -1, -1, -1};
const int dy8[8] = {0, 1, -1, 1, -1, 0, 1, -1};
const long double pi = 3.141592653589793;

#define addm(X, Y) (X) = ((X) + ((Y) % mod) + mod) % mod
#define inside(y, x, h, w) (0 <= (y) && (y) < (h) && 0 <= (x) && (x) < (w)) ? true : false

//debug
#define DEBUG

#define DUMPOUT cerr

#ifdef DEBUG
#define dump(...) DUMPOUT<<#__VA_ARGS__<<" :["<<__FUNCTION__<<":"<<__LINE__<<"]"<<endl; DUMPOUT<<"    "; dump_func(__VA_ARGS__)
#else
#define dump(...)
#endif

void dump_func() {DUMPOUT << endl;};

template <class Head, class... Tail> void dump_func(Head&& head, Tail&&... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) == 0) DUMPOUT << " ";
    else DUMPOUT << ", ";
    dump_func(std::move(tail)...);
}

//ostream
template<typename T> ostream& operator << (ostream& os, vector<T>& vec) {
    os << "["; for (int i = 0; i<vec.size(); i++) os << vec[i] << (i + 1 == vec.size() ? "" : ", "); os << "]";
    return os;
}

template<typename T, typename U> ostream& operator << (ostream& os, pair<T, U>& pair_var) {
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}

template<typename T, typename U> ostream& operator << (ostream& os, map<T, U>& map_var) {
    os << "[";
    for (auto itr = map_var.begin(); itr != map_var.end(); itr++) {
        os << "(" << itr->first << ", " << itr->second << ")"; itr++;  if(itr != map_var.end()) os << ", "; itr--;
    }
    os << "]";
    return os;
}

template<typename T> ostream& operator << (ostream& os, set<T>& set_var) {
    os << "[";
    for (auto itr = set_var.begin(); itr != set_var.end(); itr++) {
        os << *itr; ++itr; if(itr != set_var.end()) os << ", "; itr--;
    }
    os << "]";
    return os;
}

struct RollingHash {

  ll base1, base2;
  ll mod1, mod2;
  vector<ull> hash1, hash2;
  vector<ull> pow1, pow2;

  RollingHash() : base1(1009), base2(1007), mod1(999999937), mod2(1000000000 + 7) {}

  void init(const string &s) {
    int n = s.size();

    hash1.assign(n + 1, 0);
    hash2.assign(n + 1, 0);
    pow1.assign(n + 1, 1);
    pow2.assign(n + 1, 1);

    for (int i = 0; i < n; i++) {
      hash1[i + 1] = (hash1[i] + s[i]) * base1 % mod1;
      hash2[i + 1] = (hash2[i] + s[i]) * base2 % mod2;
      pow1[i + 1] = pow1[i] * base1 % mod1;
      pow2[i + 1] = pow2[i] * base2 % mod2;
    }
  }
  //[l, r) (0-indexed)
  pll get(int l, int r) {
    ll t1 = (hash1[r] - (hash1[l] * pow1[r - l]) % mod1 + mod1) % mod1;
    ll t2 = (hash2[r] - (hash2[l] * pow2[r - l]) % mod2 + mod2) % mod2;
    return make_pair(t1, t2);
  }

  bool match(int l1, int r1, int l2, int r2) {
    return get(l1, r1) == get(l2, r2) ? true : false;
  }
};

vector<int> KMPTable(const string &pt) {
    int m = pt.size();
    vector<int> nx(m + 1, -1);
    int j = -1;
    for (int i = 0; i < m; i++) {
        while (j >= 0 && pt[i] != pt[j]) {
            j = nx[j];
        }
        j += 1;
        nx[i + 1] = j;
    }
    return nx;
}

vector<int> KMPSearch (int st, const string &text, const string &pt) {
    int n = text.size(), m = pt.size();
    int start = st;
    int pt_idx = 0;
    vector<int> ret;
    vector<int> nx = KMPTable(pt);
    while (start + pt_idx < n) {
        if (text[start + pt_idx] == pt[pt_idx]) {
            pt_idx++;
            if (pt_idx == m) {
                ret.push_back(start);
                start = start + (pt_idx - nx[pt_idx]);
                pt_idx = nx[pt_idx];
            }
        }
        else {
            if (pt_idx == 0) start++;
            else {
                start = start + (pt_idx - nx[pt_idx]);
                pt_idx = nx[pt_idx];
            }
        }
    }
    return ret;
}




int n;
string s;
int cnt[26];

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n;
  cin >> s;
  rep(i, n) {
    cnt[s[i] - 'a']++;
  }
  bool pre = false;
  rep(i, 26) {
    if (cnt[i] >= 2) pre = true;
  }
  if (!pre) {
    cout << 0 << endl;
    return 0;
  }
  RollingHash rh;
  rh.init(s);
  int l = 0;
  int r = n+1;
  while (r - l > 1) {
    int len = (r + l) / 2;
    bool exist = false;
    rep(i, n) {
      if (i + len >= n) break;
      string p = "";
      rep2(j, i, i+len) p += s[j];
      vector<int> idx = KMPSearch(i+len, s, p);
      if (idx.size() >= 1) {
        exist = true;
        break;
      }
    }
    if (exist) l = len;
    else r = len;
  }
  cout << l << endl;
}


Measured memory_bytes: 512