// need
#include <iostream>
#include <algorithm>
// data structure
#include <bitset>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#include <complex>
//#include <deque>
#include <valarray>
#include <unordered_map>
#include <unordered_set>
#include <array>
// etc
#include <cassert>
#include <cmath>
#include <functional>
#include <iomanip>
#include <chrono>
#include <random>
#include <numeric>

// input
#define INIT std::ios::sync_with_stdio(false);std::cin.tie(0);
#define VAR(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__);
template<typename T> void MACRO_VAR_Scan(T& t) { std::cin >> t; }
template<typename First, typename...Rest>void MACRO_VAR_Scan(First& first, Rest& ...rest) { std::cin >> first; MACRO_VAR_Scan(rest...); }
#define VEC_ROW(type, n, ...)std::vector<type> __VA_ARGS__;MACRO_VEC_ROW_Init(n, __VA_ARGS__); for(int w_=0; w_<n; ++w_){MACRO_VEC_ROW_Scan(w_, __VA_ARGS__);}
template<typename T> void MACRO_VEC_ROW_Init(int n, T& t) { t.resize(n); }
template<typename First, typename...Rest>void MACRO_VEC_ROW_Init(int n, First& first, Rest& ...rest) { first.resize(n); MACRO_VEC_ROW_Init(n, rest...); }
template<typename T> void MACRO_VEC_ROW_Scan(int p, T& t) { std::cin >> t[p]; }
template<typename First, typename...Rest>void MACRO_VEC_ROW_Scan(int p, First& first, Rest& ...rest) { std::cin >> first[p]; MACRO_VEC_ROW_Scan(p, rest...); }
#define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)std::cin>>i;
#define MAT(type, c, m, n) std::vector<std::vector<type>> c(m, std::vector<type>(n));for(auto& R:c)for(auto& w:R)std::cin>>w;
// output
#define OUT(dist) std::cout<<(dist);
#define FOUT(n, dist) std::cout<<std::fixed<<std::setprecision(n)<<(dist);
#define SOUT(n, c, dist) std::cout<<std::setw(n)<<std::setfill(c)<<(dist);
#define SP std::cout<<" ";
#define TAB std::cout<<"\t";
#define BR std::cout<<"\n";
#define SPBR(w, n) std::cout<<(w + 1 == n ? '\n' : ' ');
#define ENDL std::cout<<std::endl;
#define FLUSH std::cout<<std::flush;
#define SHOW(dist) {std::cerr << #dist << "\t:" << (dist) << "\n";}
#define SHOWVECTOR(v) {std::cerr << #v << "\t:";for(const auto& xxx : v){std::cerr << xxx << " ";}std::cerr << "\n";}
#define SHOWVECTOR2(v) {std::cerr << #v << "\t:\n";for(const auto& xxx : v){for(const auto& yyy : xxx){std::cerr << yyy << " ";}std::cerr << "\n";}}
#define SHOWQUEUE(a) {auto tmp(a);std::cerr << #a << "\t:";while(!tmp.empty()){std::cerr << tmp.front() << " ";tmp.pop();}std::cerr << "\n";}
#define SHOWSTACK(a) {auto tmp(a);std::cerr << #a << "\t:";while(!tmp.empty()){std::cerr << tmp.top() << " ";tmp.pop();}std::cerr << "\n";}
// utility
#define ALL(a) (a).begin(),(a).end()
#define FOR(w, a, n) for(int w=(a);w<(n);++w)
#define RFOR(w, a, n) for(int w=(n)-1;w>=(a);--w)
#define REP(w, n) for(int w=0;w<int(n);++w)
#define RREP(w, n) for(int w=int(n)-1;w>=0;--w)
#define IN(a, x, b) (a<=x && x<b)
template<class T> inline T CHMAX(T & a, const T b) { return a = (a < b) ? b : a; }
template<class T> inline T CHMIN(T& a, const T b) { return a = (a > b) ? b : a; }
// test
template<class T> using V = std::vector<T>;
template<class T> using VV = V<V<T>>;

template<typename S, typename T>
std::ostream& operator<<(std::ostream& os, std::pair<S, T> p) {
	os << "(" << p.first << ", " << p.second << ")"; return os;
}

#define random_shuffle "USE std::shuffle!";

// type/const
#define int ll
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using PAIR = std::pair<int, int>;
using PAIRLL = std::pair<ll, ll>;
constexpr int INFINT = (1 << 30) - 1;                    // 1.07x10^ 9
constexpr int INFINT_LIM = (1LL << 31) - 1;              // 2.15x10^ 9
constexpr ll INFLL = 1LL << 60;                          // 1.15x10^18
constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62);  // 9.22x10^18
constexpr double EPS = 1e-10;
constexpr int MOD = 1000000007;
constexpr double PI = 3.141592653589793238462643383279;
template<class T, size_t N> void FILL(T(&a)[N], const T & val) { for (auto& x : a) x = val; }
template<class ARY, size_t N, size_t M, class T> void FILL(ARY(&a)[N][M], const T & val) { for (auto& b : a) FILL(b, val); }
template<class T> void FILL(std::vector<T> & a, const T & val) { for (auto& x : a) x = val; }
template<class ARY, class T> void FILL(std::vector<std::vector<ARY>> & a, const T & val) { for (auto& b : a) FILL(b, val); }
// ------------>8------------------------------------->8------------

struct HashData {
	int h1, h2;
	bool operator==(const HashData& rhs) const {
		return h1 == rhs.h1 && h2 == rhs.h2;
	}
	bool operator!=(const HashData& rhs) const { return !(*this == rhs); }
};
class RollingHash {
	template<int B, int M>
	class RollingHashPart {
	private:
		size_t len;
		std::vector<int> pow_b, hash;
	public:
		RollingHashPart() {}
		template<typename T>
		RollingHashPart(const T& s) : len(s.size()), pow_b(s.size() + 1), hash(s.size() + 1) {
			pow_b[0] = 1;
			hash[0] = 0;
			for (int i = 0; i < len; i++) {
				pow_b[i + 1] = (ll)pow_b[i] * B % M;
				hash[i + 1] = ((ll)hash[i] * B + s[i]) % M;
			}
		}
		// [l, r)
		int get(int l, int r) const {
			int res = (hash[r] - (ll)hash[l] * pow_b[r - l]) % M;
			if (res < 0) res += M;
			return res;
		}
	};
public:
	RollingHashPart<1033, 1000000007> rh1;
	RollingHashPart<6037, 999999937> rh2;

	RollingHash() {}
	template<typename T> RollingHash(const T & s) : rh1(s), rh2(s) {}
	// [l, r)
	HashData get(int l, int r) const {
		return HashData{ rh1.get(l, r), rh2.get(l, r) };
	}
	// [l1, r1), [l2, r2)
	int lcp(const RollingHash & rhs, int l1, int r1, int l2, int r2) const {
		int lb = 0, ub = std::min(r1 - l1, r2 - l2) + 1;
		while (ub - lb > 1) {
			int md = (lb + ub) >> 1;
			(get(l1, l1 + md) == rhs.get(l2, l2 + md) ? lb : ub) = md;
		}
		return lb;
	}
};

signed main() {
	INIT;

	VAR(int, n);
	VAR(std::string, s);

	RollingHash rh(s);
	auto check = [&](int d) {
		REP(i, n) FOR(j, i + d, n - d + 1) {
			if (s[i] != s[j]) continue;
			if (rh.get(i, i + d) == rh.get(j, j + d)) return true;
		}
		return false;
	};

	int ok = 0, ng = n / 2 + 2;
	while (ng - ok > 1) {
		int me = (ok + ng) / 2;
		if (check(me)) ok = me;
		else ng = me;
	}
	OUT(ok)BR;

	return 0;
}

Measured memory_bytes: 384