#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using VI = vector<ll>;
using VV = vector<VI>;
using VS = vector<string>;

// tourist set
template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string& s) {
  return '"' + s + '"';
}

string to_string(const char* s) {
  return to_string((string) s);
}

string to_string(bool b) {
  return (b ? "true" : "false");
}

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
// tourist set end

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i,b) FOR(i, 0, b)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("YES")
#define p_no() p("NO")
#define pb(s) push_back(s)
#define SZ(x) ((int)(x).size())

void no(){p_no(); exit(0);}
void yes(){p_yes(); exit(0);}

const ll mod = 1e9 + 7;
const ll inf = 1e18;

void vprint(vector<ll> A){
    ll L = A.size();
    FOR(i, 0, L){
        if(i) cout << ' ';
        cout << A[i];
    }
    cout << endl;
}

// 重なっていないペアがあるか
bool find_pair(vector<pair<ll,ll>>& V){
  if(V.size()<=1) return false;
  ll L = V.size();
  // 全探索
  rep(i, L){
    FOR(j, i+1, L){
      if(V[i].second < V[j].first) return true;
    }
  }
  return false;

}

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 >;
const ll seed = 1e11+7;
using RH2 = RollingHash< seed >;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll N; cin >> N;
    string s; cin >> s;

    // 存在しない場合をチェック
    map<char, ll> mp;
    for(char c : s){
      mp[c]++;
    }
    if(mp.size()==N){
      p(0);
      return 0;
    }

    RH rh(s);
    RH rh2(s, 9973);

    ll left = 1; // can
    ll right = N/2+1; // can't

    ll ma = 0;
    while(left+1!=right){
      ll L = (left+right)/2; // この長さで見つけられるか
      bool found = false;
      FOR(i, 0, N){
        FOR(j, i+L, N){
          if(found) break;
          if(j+L>N) continue;
          ll hash0 = rh.get(i, i+L);
          ll hash1 = rh.get(j, j+L);

          // ll h0 = rh2.get(i, i+L);
          // ll h1 = rh2.get(j, j+L);


          if(hash0==hash1 && s.substr(i, L)==s.substr(j, L)){
            found = true;
            chmax(ma, L);
          }
        }
      }
      if(found){
        left = L;
      }else{
        right = L;
      }
    }

    p(ma);
    return 0;
}

Measured memory_bytes: 384