// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;

#define Rep(i,n) for(int i=0;i<(int)(n);i++)

#define For(i,n1,n2) for(int i=(int)(n1);i<(int)(n2);i++)

#define REP(i,n) for(ll i=0;i<(ll)(n);i++)

#define RREP(i,n) for(ll i=((ll)(n)-1);i>=0;i--)

#define FOR(i,n1,n2) for(ll i=(ll)(n1);i<(ll)(n2);i++)

#define RFOR(i,n1,n2) for(ll i=((ll)(n1)-1);i>=(ll)(n2);i--)

#define all(a)  (a).begin(),(a).end()

#define SORT(a) sort((a).begin(),(a).end())

#define oorret 0

#define oor(x) [&](){try{x;} catch(const out_of_range& oor){return oorret;} return x;}()

#define IOS cin.tie(0),ios::sync_with_stdio(false)

typedef long long ll;

typedef unsigned long long ull;

typedef pair<ll, ll> P;

template<typename T1, typename T2> inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return 1; }return 0; }

template<typename T1, typename T2> inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return 1; }return 0; }

template<class Type>struct is_vector : std::false_type {};

template<class ValueType, class Alloc>struct is_vector<std::vector<ValueType, Alloc>> : std::true_type {};

template <typename T> inline ostream& operator << (ostream& out, const vector<T>& v) {

	if (v.empty())return out;

	constexpr bool is_vector_v = is_vector<T>::value;

	if (is_vector_v)for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? "\n" : "");

	else for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? " " : "");

	return out;

}

inline void put() {}

template<class T> inline void put(const T& first) { std::cout << first << "\n"; }

template<class T, class... N> inline void put(const T& first, const N& ... rest) { std::cout << first << " "; put(rest...); }

inline void putn() {}

template<class T, class... N> inline void putn(const T& first, const N& ... rest) { std::cout << first << "\n"; putn(rest...); }



template <uint_fast64_t basesize>

class RollingHash {

public:

	using u64 = uint_fast64_t;

	using i32 = int_fast32_t;

	using arr = array<u64, basesize>;

	const u64 mod = (1ull << 61) - 1;

	const u64 m30 = (1ull << 30) - 1;

	const u64 m31 = (1ull << 31) - 1;

	const u64 p31 = (1ull << 31);

	arr base;

	RollingHash() {

		random_device seed_gen;

		mt19937_64 engine(0);

		for (u64 i = 0; i < basesize; ++i) {

			base[i] = (engine() & m30) + m30;

		}

	}

	u64 mul(u64 a, u64 b) {

		u64 au = a >> 31;

		u64 ad = a & m31;

		u64 bu = b >> 31;

		u64 bd = b & m31;

		u64 mid = ad * bu + au * bd;

		u64 midu = mid >> 30;

		u64 midd = mid & m30;

		u64 res = au * bu * 2 + midu + (midd << 31) + ad * bd;

		return res;

	}

	u64 calcMod(u64 v) {

		v = (v & mod) + (v >> 61);

		if (v > mod)v - mod;

		return v;

	}

	vector<arr> calcHash(string &s,i32 l,i32 r) { // s[l,r)のhashを計算

		if (l >= r) {

			vector<arr> res(0);

			return res;

		}

		vector<arr> res(r - l);

		for (i32 j = 0; j < basesize ; ++j) {

			res[0][j] = s[l];

		}

		for (i32 i = 1; i < r - l; ++i) {

			for (i32 j = 0; j < basesize; ++j) {

				res[i][j] = calcMod(mul(res[i - 1][j], base[j]) + s[i + l]);

			}

		}

		return res;

	}

	vector<arr> calcHashLen(string& s, i32 len) {

		i32 l = (i32)s.size() - len + 1;

		vector<arr> pre = calcHash(s, 0, len);

		vector<arr> res(l);

		const u64 pos = mod * 3;

		arr p;

		fill(p.begin(), p.end(), 1);

		if (0 < len) {

			for (i32 j = 0; j < basesize; ++j) {

				res[0][j] = pre[len - 1][j];

			}

		}

		for (i32 i = 0; i < len; ++i) {

			for (i32 j = 0; j < basesize; ++j) {

				p[j] = calcMod(mul(p[j], base[j]));

			}

		}

		for (i32 i = 1; i < l; ++i) {

			for (i32 j = 0; j < basesize; ++j) {

				res[i][j] = calcMod(mul(res[i - 1][j], base[j]) + s[i - 1 + len]);

				res[i][j] = calcMod(res[i][j] + pos - mul(s[i - 1], p[j]));				

			}

		}

		return res;

	}

};



constexpr uint_fast64_t  bs = 1000;

using arr = array<uint_fast64_t, bs>;

using rh = RollingHash<bs>;



int main() {

	IOS;

	int n;

	string s;

	cin >> n >> s;

	rh r;

	

	int lb = -1, ub = n + 1;

	while (ub - lb > 1) {

		int mid = (ub + lb) / 2;

		multiset<arr> st;

		auto ha = r.calcHashLen(s, mid);

		bool flag = false;

		FOR(i, mid, ha.size()) {

			st.insert(ha[i]);

		}

		REP(i, ha.size()) {

			auto itr = st.find(ha[i]);

			if (itr != st.end()) {

				flag = true;

				break;

			}

			if (i + mid < ha.size()) {

				st.erase(st.find(ha[i + mid]));

			}

			if (i - mid >= 0) {

				st.insert(ha[i - mid]);

			}			

		}

		if (flag) {

			lb = mid;

		} else {

			ub = mid;

		}

	}

	put(lb);

	return 0;

}


// Faster C++ solution for the same problem (measured speedup: 1.4872850335538854x):
#include <bits/stdc++.h>

using namespace std;

#define Rep(i,n) for(int i=0;i<(int)(n);i++)

#define For(i,n1,n2) for(int i=(int)(n1);i<(int)(n2);i++)

#define REP(i,n) for(ll i=0;i<(ll)(n);i++)

#define RREP(i,n) for(ll i=((ll)(n)-1);i>=0;i--)

#define FOR(i,n1,n2) for(ll i=(ll)(n1);i<(ll)(n2);i++)

#define RFOR(i,n1,n2) for(ll i=((ll)(n1)-1);i>=(ll)(n2);i--)

#define all(a)  (a).begin(),(a).end()

#define SORT(a) sort((a).begin(),(a).end())

#define oorret 0

#define oor(x) [&](){try{x;} catch(const out_of_range& oor){return oorret;} return x;}()

#define IOS cin.tie(0),ios::sync_with_stdio(false)

typedef long long ll;

typedef unsigned long long ull;

typedef pair<ll, ll> P;

template<typename T1, typename T2> inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return 1; }return 0; }

template<typename T1, typename T2> inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return 1; }return 0; }

template<class Type>struct is_vector : std::false_type {};

template<class ValueType, class Alloc>struct is_vector<std::vector<ValueType, Alloc>> : std::true_type {};

template <typename T> inline ostream& operator << (ostream& out, const vector<T>& v) {

	if (v.empty())return out;

	constexpr bool is_vector_v = is_vector<T>::value;

	if (is_vector_v)for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? "\n" : "");

	else for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? " " : "");

	return out;

}

inline void put() {}

template<class T> inline void put(const T& first) { std::cout << first << "\n"; }

template<class T, class... N> inline void put(const T& first, const N& ... rest) { std::cout << first << " "; put(rest...); }

inline void putn() {}

template<class T, class... N> inline void putn(const T& first, const N& ... rest) { std::cout << first << "\n"; putn(rest...); }



template <uint_fast64_t basesize>

class RollingHash {

public:

	using u64 = uint_fast64_t;

	using i32 = int_fast32_t;

	using arr = array<u64, basesize>;

	const u64 mod = (1ull << 61) - 1;

	const u64 m30 = (1ull << 30) - 1;

	const u64 m31 = (1ull << 31) - 1;

	const u64 p31 = (1ull << 31);

	arr base;

	RollingHash() {

		random_device seed_gen;

		mt19937_64 engine(seed_gen());

		for (u64 i = 0; i < basesize; ++i) {

			base[i] = (engine() & m30) + m30;

		}

	}

	u64 mul(u64 a, u64 b) {

		u64 au = a >> 31;

		u64 ad = a & m31;

		u64 bu = b >> 31;

		u64 bd = b & m31;

		u64 mid = ad * bu + au * bd;

		u64 midu = mid >> 30;

		u64 midd = mid & m30;

		u64 res = au * bu * 2 + midu + (midd << 31) + ad * bd;

		return res;

	}

	u64 calcMod(u64 v) {

		v = (v & mod) + (v >> 61);

		if (v > mod)v - mod;

		return v;

	}

	vector<arr> calcHash(string& s, i32 l, i32 r) { // s[l,r)のhashを計算

		if (l >= r) {

			vector<arr> res(0);

			return res;

		}

		vector<arr> res(r - l);

		for (i32 j = 0; j < basesize; ++j) {

			res[0][j] = s[l];

		}

		for (i32 i = 1; i < r - l; ++i) {

			for (i32 j = 0; j < basesize; ++j) {

				res[i][j] = calcMod(mul(res[i - 1][j], base[j]) + s[i + l]);

			}

		}

		return res;

	}

	vector<arr> calcHashLen(string& s, i32 len) {

		i32 l = (i32)s.size() - len + 1;

		vector<arr> pre = calcHash(s, 0, len);

		vector<arr> res(l);

		const u64 pos = mod * 3;

		arr p;

		fill(p.begin(), p.end(), 1);

		if (0 < len) {

			for (i32 j = 0; j < basesize; ++j) {

				res[0][j] = pre[len - 1][j];

			}

		}

		for (i32 i = 0; i < len; ++i) {

			for (i32 j = 0; j < basesize; ++j) {

				p[j] = calcMod(mul(p[j], base[j]));

			}

		}

		for (i32 i = 1; i < l; ++i) {

			for (i32 j = 0; j < basesize; ++j) {

				res[i][j] = calcMod(mul(res[i - 1][j], base[j]) + s[i - 1 + len]);//添え字周りが怪しい

				res[i][j] = calcMod(res[i][j] + pos - mul(s[i - 1], p[j]));

			}

		}

		return res;

	}

};



constexpr uint_fast64_t  bs = 50;

using arr = array<uint_fast64_t, bs>;

using rh = RollingHash<bs>;



int main() {

	IOS;

	int n;

	string s;

	cin >> n >> s;

	rh r;



	int lb = -1, ub = n + 1;

	while (ub - lb > 1) {

		int mid = (ub + lb) / 2;

		multiset<arr> st;

		auto ha = r.calcHashLen(s, mid);

		bool flag = false;

		FOR(i, mid, ha.size()) {

			st.insert(ha[i]);

		}

		REP(i, ha.size()) {

			auto itr = st.find(ha[i]);

			if (itr != st.end()) {

				flag = true;

				break;

			}

			if (i + mid < ha.size()) {

				st.erase(st.find(ha[i + mid]));

			}

			if (i - mid >= 0) {

				st.insert(ha[i - mid]);

			}

		}

		if (flag) {

			lb = mid;

		} else {

			ub = mid;

		}

	}

	put(lb);

	return 0;

}