#include <bits/stdc++.h>
#define LLI long long int
#define FOR(v, a, b) for(LLI v = (a); v < (b); ++v)
#define FORE(v, a, b) for(LLI v = (a); v <= (b); ++v)
#define REP(v, n) FOR(v, 0, n)
#define REPE(v, n) FORE(v, 0, n)
#define REV(v, a, b) for(LLI v = (a); v >= (b); --v)
#define ALL(x) (x).begin(), (x).end()
#define RALL(x) (x).rbegin(), (x).rend()
#define ITR(it, c) for(auto it = (c).begin(); it != (c).end(); ++it)
#define RITR(it, c) for(auto it = (c).rbegin(); it != (c).rend(); ++it)
#define EXIST(c,x) ((c).find(x) != (c).end())
#define fst first
#define snd second
#define popcount __builtin_popcount
#define UNIQ(v) (v).erase(unique(ALL(v)), (v).end())
#define bit(i) (1LL<<(i))

#ifdef DEBUG
#include <misc/C++/Debug.cpp>
#else
#define dump(...) ((void)0)
#endif

#define gcd __gcd

using namespace std;
template <class T> constexpr T lcm(T m, T n){return m/gcd(m,n)*n;}

template <typename I> void join(ostream &ost, I s, I t, string d=" "){for(auto i=s; i!=t; ++i){if(i!=s)ost<<d; ost<<*i;}ost<<endl;}
template <typename T> istream& operator>>(istream &is, vector<T> &v){for(auto &a : v) is >> a; return is;}

template <typename T, typename U> bool chmin(T &a, const U &b){return (a>b ? a=b, true : false);}
template <typename T, typename U> bool chmax(T &a, const U &b){return (a<b ? a=b, true : false);}
template <typename T, size_t N, typename U> void fill_array(T (&a)[N], const U &v){fill((U*)a, (U*)(a+N), v);}

struct Init{
  Init(){
    cin.tie(0);
    ios::sync_with_stdio(false);
  }
}init;

template <typename T, LLI BASE, LLI MOD> class RollingHash{
private:
  static vector<LLI> pow;

public:
  static void init(int N){
    pow.assign(N+1,0);
    pow[0] = 1;
    FORE(i,1,N){
      pow[i] = pow[i-1]*BASE % MOD;
    }
  }

  static vector<LLI> generate_hash(const T &s){
    vector<LLI> ret(s.size()+1);

    FORE(i,1,(int)s.size()){
      ret[i] = (ret[i-1]*BASE+s[i-1]) % MOD;
    }
    
    return ret;
  }

  static LLI hash(const vector<LLI> &shash, int i, int j){ // [i, j)
    return (shash[j] - shash[i] * pow[j-i] + MOD*MOD) % MOD;
  }

  static LLI hash(const T &p){
    LLI phash = 0;
    REP(i,(int)p.size()) phash = (phash*BASE+p[i]) % MOD;
    return phash;
  }

  
  static vector<int> find(const vector<LLI> &shash, const T &p){
    vector<int> ret;
    int pl = p.size();
    LLI phash = hash(p);
    REP(i,(int)shash.size()-pl) if(hash(shash,i,i+pl) == phash) ret.push_back(i);
    return ret;
  }
};

template <typename T, LLI BASE, LLI MOD> vector<LLI> RollingHash<T,BASE,MOD>::pow;

using R1 = RollingHash<string,31,1000000009>;
using R2 = RollingHash<string,41,998244353>;

int main(){
  R1::init(10000);
  R2::init(10000);
  
  int N;
  string s;
  while(cin >> N >> s){

    auto hs1 = R1::generate_hash(s);
    auto hs2 = R2::generate_hash(s);
    
    int ans = 0;

    auto check =
      [&](int L){
        set<pair<LLI,LLI>> store;
        queue<pair<LLI,LLI>> q;

        REP(i,N-L+1){
          auto h1 = R1::hash(hs1,i,i+L);
          auto h2 = R2::hash(hs2,i,i+L);
        
          pair<LLI,LLI> H(h1,h2);

          if(EXIST(store,H)){
            return true;
          }

          if((int)q.size() == L-1){
            q.push(H);
            auto t = q.front(); q.pop();
            store.insert(t);
          }else{
            q.push(H);
          }
        }

        return false;
      };

    int lb = 0, ub = N, mid;
    while(abs(lb-ub) > 1){
      mid = (lb+ub)/2;

      if(check(mid)){
        lb = mid;
      }else{
        ub = mid;
      }
    }

    ans = lb;

    cout << ans << endl;
  }


  return 0;
}


Measured memory_bytes: 896