#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;

#define REP(i,n) for(long long i = 0; i < (n); i++)
#define FOR(i, m, n) for(long long i = (m);i < (n); ++i)
#define ALL(obj) (obj).begin(),(obj).end()
#define SPEED cin.tie(0);ios::sync_with_stdio(false);

template<class T> using V = vector<T>;
template<class T, class U> using P = pair<T, U>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQR = priority_queue<T,vector<T>,greater<T>>;

constexpr long long MOD = (long long)1e9 + 7;
constexpr long long MOD2 = 998244353;
constexpr long long HIGHINF = (long long)1e18;
constexpr long long LOWINF = (long long)1e15;
constexpr long double PI = 3.1415926535897932384626433;

template <class T> vector<T> multivector(size_t N,T init){return vector<T>(N,init);}
template <class... T> auto multivector(size_t N,T... t){return vector<decltype(multivector(t...))>(N,multivector(t...));}
template <class T> void corner(bool flg, T hoge) {if (flg) {cout << hoge << endl; exit(0);}}
template <class T, class U>ostream &operator<<(ostream &o, const map<T, U>&obj) {o << "{"; for (auto &x : obj) o << " {" << x.first << " : " << x.second << "}" << ","; o << " }"; return o;}
template <class T>ostream &operator<<(ostream &o, const set<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const multiset<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const vector<T>&obj) {o << "{"; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "}"; return o;}
template <class T, class U>ostream &operator<<(ostream &o, const pair<T, U>&obj) {o << "{" << obj.first << ", " << obj.second << "}"; return o;}
template <template <class tmp>  class T, class U> ostream &operator<<(ostream &o, const T<U> &obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr)o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
void print(void) {cout << endl;}
template <class Head> void print(Head&& head) {cout << head;print();}
template <class Head, class... Tail> void print(Head&& head, Tail&&... tail) {cout << head << " ";print(forward<Tail>(tail)...);}
template <class T> void chmax(T& a, const T b){a=max(a,b);}
template <class T> void chmin(T& a, const T b){a=min(a,b);}
void YN(bool flg) {cout << (flg ? "YES" : "NO") << endl;}
void Yn(bool flg) {cout << (flg ? "Yes" : "No") << endl;}
void yn(bool flg) {cout << (flg ? "yes" : "no") << endl;}


class RollingHash {
private:
    long long base1,base2;
    long long mod1,mod2;
    vector<long long> hash1,hash2,pow1,pow2;
 
public: 
    RollingHash(const string& S) : base1(1009), base2(1007), mod1(1000000007), mod2(1000000009) {
        int N = S.size();
        hash1.resize(N+1,0);
        hash2.resize(N+1,0);
        pow1.resize(N+1,1);
        pow2.resize(N+1,1);
 
        for(int i=1; i<=N; ++i) {
            hash1[i] = ((hash1[i-1]+S[i-1]) * base1) % mod1;
            hash2[i] = ((hash2[i-1]+S[i-1]) * base2) % mod2;
            pow1[i] = (pow1[i-1] * base1) % mod1;
            pow2[i] = (pow2[i-1] * base2) % mod2;
        }
    }

	//[l,r)
    pair<long long, long long> get(int l,int r) {
        long long t1 = ((hash1[r] - hash1[l] * pow1[r-l]) % mod1 + mod1) % mod1;
        long long t2 = ((hash2[r] - hash2[l] * pow2[r-l]) % mod2 + mod2) % mod2;
        return {t1,t2};
    }
};

int main(){
	int N; cin >> N;
	string S; cin >> S;
    RollingHash RH(S);
    int ok = 0,ng = N,md;
    while(ng-ok>1){
        md = (ok+ng)>>1;
        map<pair<ll,ll>,int> mp;
        int flg = 0;
        for(int i = md; i+md<=N;++i) {
            mp[RH.get(i-md,i)]++;
            if(mp[RH.get(i,i+md)]) flg = 1;
        }
        (flg?ok:ng)=md;
    }
    cout << ok << endl;
}


Measured memory_bytes: 768