#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
#pragma warning(disable : 4996)
#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>
#include<numeric>
#include<cstring>
#include<cstdio>
#include<functional>
#include<bitset>
#include<limits.h>
#include<cassert>
#include<iterator>
#include<complex>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<time.h>
#include<random>
#include<array>


using namespace std;

#define REP(i, n) for(int i = 0;i < n;++i)
#define REPR(i, n) for(int i = n-1;i >= 0;--i)
#define FOR(i, m, n) for(int i = m;i < n;++i)
#define FORR(i, m, n) for(int i = m-1;i >= n;--i)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define REVERSE(v,n) reverse(v,v+n);
#define VREVERSE(v) reverse(v.begin(), v.end())
#define ll long long
#define print(x) cout<<(x)<<'\n'
#define pe(x) cout<<(x)<<" "
#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define lb(v,n) lower_bound(v.begin(), v.end(), (n))
#define ub(v,n) upper_bound(v.begin(), v.end(), (n))
//#define int long long
//#define double long double
#define all(x) (x).begin(), (x).end()
#define print_space(v) REP(i,v.size())cout << v[i] << ((i == v.size() - 1) ? "\n" : " ")
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; }
typedef pair<int, int>pii;
typedef array<int, 3> arr3;
std::random_device rd;
std::mt19937 mt(rd());
uint32_t getrand() {uint32_t seed = time(NULL);mt.seed(seed);return mt();}
//constexpr ll MOD = 1e9 + 7;
constexpr int MAX = 2000020;
const double pi = acos(-1); constexpr double EPS = 1e-8;
constexpr ll INF = 1e18;
void y(bool c) {if (c)print("Yes"); else print("No");}
using ul = unsigned long long;
constexpr ul MASK30 = (1UL << 30) - 1;
constexpr ul MASK31 = (1UL << 31) - 1;
constexpr ul MOD = (1UL << 61) - 1;
constexpr ul MASK61 = MOD;
//mod 2^61-1を計算する関数
ul CalcMod(ul x)
{
	ul xu = x >> 61;
	ul xd = x & MASK61;
	ul res = xu + xd;
	if (res >= MOD) res -= MOD;
	return res;
}
//a*b mod 2^61-1を返す関数(最後にModを取る)
ul Mul(ul a, ul b)
{
	ul au = a >> 31;
	ul ad = a & MASK31;
	ul bu = b >> 31;
	ul bd = b & MASK31;
	ul mid = ad * bu + au * bd;
	ul midu = mid >> 30;
	ul midd = mid & MASK30;
	return CalcMod(au * bu * 2 + midu + (midd << 31) + ad * bd);
}

struct RollingHash {
	vector<ul>hash;
	vector<ul>p;
	ul B;
	RollingHash(const string &s, ul B_) :B(B_) {
		int N = s.size();
		hash.assign(N + 1, 0);
		p.assign(N + 1, 1);
		for (int i = 0; i < N; i++) {
			hash[i + 1] = CalcMod(Mul(hash[i], B) + s[i]);
			p[i + 1] = CalcMod(Mul(p[i], B));
		}
	}

	ul find(int l, int r) {
		return CalcMod(hash[r] + MOD * 3 - Mul(hash[l], p[r - l]));
	}
};

void solve() {
	ul base = getrand() % 100007;
	int N; string S; cin >> N >> S;
	RollingHash rh(S, base);
	ll ok = 0, ng = N / 2 + 1;
	while (ng - ok > 1) {
		int mid = (ok + ng) / 2;
		bool possible = false;
		REP(i, N - 2 * mid + 1) {
			FOR(j, i + mid, N - mid + 1) {
				if (rh.find(i, i + mid) == rh.find(j, j + mid)) {
					possible = true;
					goto END;
				}
			}
		}
	END:;
		if (possible)ok = mid; else ng = mid;
	}
	print(ok);
}

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	//int q; cin >> q;
	//while (q--)
	solve();
}




Measured memory_bytes: 512