#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= int(n); i++)
#define rreps(i, n) for (int i = int(n); i >= 1; i--)
#define repc(i, n) for (int i = 0; i <= int(n); i++)
#define rrepc(i, n) for (int i = int(n); i >= 0; i--)
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define repic(i, a, b) for (int i = int(a); i <= int(b); i++)
#define each(x, y) for (auto &x : y)
#define all(a) (a).begin(), (a).end()
#define bit32(x) (1 << (x))
#define bit64(x) (1ll << (x))

using namespace std;

using i32 = int;
using i64 = long long;
using u64 = unsigned long long;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;
using vu64 = vector<u64>;
using vf80 = vector<f80>;
using vstr = vector<string>;

inline void yes() { cout << "Yes" << '\n'; exit(0); }
inline void no() { cout << "No" << '\n'; exit(0); }
inline i64 gcd(i64 a, i64 b) { if (min(a, b) == 0) return max(a, b); if (a % b == 0) return b; return gcd(b, a % b); }
inline i64 lcm(i64 a, i64 b) { if (min(a, b) == 0) return max(a, b); return a / gcd(a, b) * b; }
inline u64 xorshift() { static u64 x = 88172645463325252ull; x = x ^ (x << 7); return x = x ^ (x >> 9); }
template <typename T> class pqasc : public priority_queue<T, vector<T>, greater<T>> {};
template <typename T> class pqdesc : public priority_queue<T, vector<T>, less<T>> {};
template <typename T> inline void amax(T &x, T y) { if (x < y) x = y; }
template <typename T> inline void amin(T &x, T y) { if (x > y) x = y; }
template <typename T> inline T exp(T x, i64 n, T e = 1) { T r = e; while (n > 0) { if (n & 1) r *= x; x *= x; n >>= 1; } return r; }
template <typename T> inline T bis(T ok, T ng, function<bool(T)> f, T eps = 1) { while (abs(ok - ng) > eps) { T mi = (ok + ng) / 2; (f(mi) ? ok : ng) = mi; } return ok; }
template <typename T> istream& operator>>(istream &is, vector<T> &v) { each(x, v) is >> x; return is; }
template <typename T> ostream& operator<<(ostream &os, vector<T> &v) { rep(i, v.size()) { if (i) os << ' '; os << v[i]; } return os; }
void solve(); int main() { ios::sync_with_stdio(0); cin.tie(0); cout << fixed << setprecision(16); solve(); return 0; }

struct RollingHash {
  const int h = 1000000007;
  const int b = 10007;
  vector<int> ha;
  vector<int> po;
  RollingHash(const string &s) {
    int n = (int) s.size();
    ha.assign(n + 1, 0);
    po.assign(n + 1, 1);
    for (int i = 0; i < n; i++) {
      ha[i + 1] = ((long long) ha[i] * b + s[i]) % h;
      po[i + 1] = ((long long) po[i] * b) % h;
    }
  }
  int get(int l, int r) {
    return (ha[r] + h - ((long long) ha[l] * po[r - l]) % h) % h;
  }
};

void solve() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  int ok = 0, ng = n + 1;
  auto rh = RollingHash(s);
  while (ng - ok > 1) {
    int md = (ok + ng) / 2;
    bool f = false;
    map<int, int> se;
    for (int i = 0; i + md <= n; i++) {
      int key = rh.get(i, i + md);
      if (se.count(key)) {
        if (se[key] <= i - md) {
          f = true;
        }
      } else {
        se[key] = i;
      }
    }
    (f ? ok : ng) = md;
  }
  cout << ok << endl;
}


Measured memory_bytes: 512