#include <bits/stdc++.h>
#include <algorithm>
#include <cmath>
#include <set>
#include <cstdio>
#include <vector>
#include <iostream>
#include <utility>
#include <queue>
#include <map>
#include <complex>
#define fir first
#define sec second
#define sz(s) (s).size()
#define pb push_back
#define get(n) scanf("%d",&n);
#define gets(s) string s;cin >> (s);
#define prfi(n) printf("%d", &n);
#define prfd(n) printf("%lf", &n);
#define All(s) (s).begin(), (s).end()
#define rep(i,j) for(int (i)=0;(i)<(j);(i)++)
#define For(i,j,k) for(int (i)=(j);(i)<(k);(i)++)
#define drep(i,j) for(int (i)=(j);(i)>=0;(i)--)
#define Ford(i,j,k) for(int (i)=(j);i>=(k);i--)
#define fore(c,v) for(auto (c): (v))
#define lp for(int __=0;__<n;i++)
#define mem(a,b) memset(a,b,sizeof(a));
#define dump(x)  std::cout << #x << " = " << (x) << std::endl;
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
using ull = unsigned long long int;
using ll = long long;
using ld = long double;
using pii = std::pair<int,int>;
using pll = std::pair<ll, ll>;
using vi = std::vector<int> ;
using vvi = std::vector<vi> ;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vd = std::vector<double> ;
using vvd = std::vector<vd> ;
using qi = std::queue<int> ;
using vpii = std::vector<std::pair<int, int> >;
using vpll = std::vector<pll>;
using namespace std;

const int Mod = (1e9) + 7;
const int INF = 1e9 + 19;
const ll INFL = 1e18 + 19;
const int dx[] = {-1, 0, 0, 1};
const int dy[] = {0, -1, 1, 0};
const int dx2[] = {-1, -1, -1, 0, 0, 0, 1, 1, 1};
const int dy2[] = {1, 0, -1, 1, 0, -1, 1, 0, -1};
const double EPS = 1e-10;
//_____________________________________Templates_________________________________________//

template<class T1, class T2> inline void chmin(T1 &a, T2 b){if(a > b) a = b;}
template<class T1, class T2> inline void chmax(T1 &a, T2 b){if(a < b) a = b;}
template<class T> inline void pri(T a){cout << a << endl;}
template<class Z> using vec = vector<Z>;
template<class T> using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
//mainly use for dynamic prog
template<class T1, class T2>
void update(T1 &a, T2 b){
  a += b;
  if(a > Mod) a %= Mod;
}

inline void IN(void){
  return;
}

template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}

inline void OUT(void){
  cout << "\n";
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}

bool pairsort(pll pl, pll pr){
  if(pl.first == pr.first)return pl.second > pr.second;
  return pl.first < pr.first;
}

int cntbit(ll a,int n,int j){int res = 0;For(i,j,n){if(a>>i & 1){res++;}}return res;}
vector<int> make_bit(int a){vector<int> res; for(int i=31;i>=0;i--)if(a&(1<<i))res.pb(i);return res;}
bool stdbit(int a, int b){return a&(1 << b); }
int GCD(int a, int b){if(b > a)return GCD(b,a);if(a%b == 0)return b;else return GCD(b, a%b);}
int LCM(int a, int b){return a*b/GCD(a,b);}
int roundup(int a, int b){if(a % b == 0)return a/b;else return (a+b)/b;}
int rounddown(int a, int b){if(a%b == 0)return a/b;else {return (a-b)/b;}}
ll pow(ll a, ll n){ll res = 1;while(n > 0){if(n&1)res *= a; a *= a; n = n >> 1;}return res;}
ll GetDiviserCount(ll N)//約数の個数
{
  ll res = 1;
  For(i,2,sqrt(N)+1)
  {
    ll cnt = 0;
    while(N%i == 0)
    {
      cnt++;
      N /= i;
    }
    res *= (cnt + 1);
    if(N == 1)break;
  }
  if(N != 1)res *= 2;
  return res;
}
vll GetDivisor(ll N)//約数列挙
{
  vll res;
  for(ll i = 1;i*i <= N;i++)
  {
    if(N%i == 0)
    {
      res.pb(i);
      if(i*i != N)res.pb(N/i);
    }
  }
  sort(All(res));
  return res;
}


struct Modint
{
  using ll = long long int;
  ll x;
  Modint(ll x=0) :x((x%Mod+Mod)%Mod) {}
  Modint operator - ()
  {
   return Modint(-x);
  }
  Modint& operator +=(Modint a)
  {
    (x += a.x%Mod)%Mod;
    return *this;
  }
  Modint& operator -=(Modint a)
  {
   x = (x - a.x + Mod)%Mod;
   return *this;
  }
  Modint& operator *=(Modint a)
  {
    (x *= a.x) %= Mod;
    return *this;
  }
  Modint operator + (Modint a)
  {
    Modint b(*this);
    b += a;
    return b;
  }
  Modint operator - (Modint a)
  {
    Modint b(*this);
    b -= a;
    return b;
  }
  Modint operator * (Modint a)
  {
    Modint b(*this);
    b *= a;
    return b;
  }
  long long int EXTGCD(long long int a, long long int b, long long int &x, long long int &y)
  {
    if(b==0)
    {
      x = 1;
      y = 0;
      return a;
    }
    long long int g = EXTGCD(b,a%b,y,x);
    y -= (a/b)*x;
    return g;
  }
  Modint inverse()
  {
    long long int a,b;
    EXTGCD(x,Mod,a,b);
    (a += Mod)%=Mod;
    return a;
  }
  Modint pow(ll a)
  {
    Modint res = 1;
    Modint b = x;
    while(a > 0)
    {
      if(a & 1)res *= b;
      a = a >> 1;
      b *= b;
    }
    return res;
  }
  friend ostream& operator<<(ostream& os, const Modint& a);
};
ostream& operator<< (ostream& os, const Modint& a)
{
  os << a.x;
  return os;
}
struct combination
{
  vector<Modint> fact,ifact;
  combination(int n) : fact(n+1), ifact(n+1)
  {
    fact[0] = 1;
    for(int i=1;i<=n;i++)fact[i] = fact[i-1] * i;
    ifact[n] = fact[n].inverse();
    for(int i=n;i>=1;i--)ifact[i-1] = ifact[i] * i;
  }
  Modint operator() (int n,int k)
  {
    return fact[n]*ifact[n-k]*ifact[k];
  }
};
using vm = vector<Modint>;
using vvm = vector<vm>;
template<class Z>
struct MyMatrix
{
  using mat = MyMatrix<Z>;
  vector<vector<Z>> m_dat;
  int m_h;
  int m_w;
  MyMatrix(int h, int w) : m_h(h), m_w(w) ,m_dat(h,vector<Z>(w)) {}
  vector<Z> &operator[] (int idx)
  {
    return m_dat[idx];
  }
  mat Multiple(mat &a)
  {
    mat C(m_h, a.m_w);
    for(int i=0;i<m_h;i++)
    {
      for(int j=0;j<a.m_w;j++)
      {
        for(int k=0;k<m_w;k++)
        {
         C[i][j] += m_dat[i][k] * a[k][j];
        }
      }
    }
    return C;
  }
  mat Pow(ll x)
  {
    mat B(m_h,m_w);
    for(int i=0;i<m_h;i++)
    {
      B[i][i] = 1;
    }
    mat A = *this;
    while(x > 0)
    {
      if(x&1)B = B.Multiple(A);
      A = A.Multiple(A);
      x = x >> 1;
    }
    return B;
  }
  //friend ostream& operator<<(ostream &os, const mat &A);
};
/*
template<class Z>
ostream& operator<<(ostream &os, Matrix<Z>& A)
{
  for(int i=0;i<A.m_h;i++)
  {
    for(int j=0;j<A.m_w;j++)
    {
      os << A[i][j] << " ";
    }
    os << endl;
  }
  return os;
}
*/
template<class T>
using mat = MyMatrix<T>;
//_____________________　following sorce code_________________________//
const int max_n = 3 * (1e5) + 1;
const int max_m = 83 * (1e5) + 1;

int n,m,k;
ll N;
int h,w;
string S;
int a,b,c;
vi v;
int ans;
double x,y,z;
vector<int> G[1010101];

const unsigned long long int B1 = 1000000007;
const unsigned long long int B2 = 10000000007;
bool RollingHash(string const &S,string const &T)
{
  int slen = S.length();
  int tlen = T.length();
  if(tlen > slen)return false;
  unsigned long long int t1 = 1;
  unsigned long long int t2 = 1;
  for(int i=0;i<tlen;i++)
  {
    t1 *= B1;
    t2 *= B2;
  }
  unsigned long long int sh1 = 0;
  unsigned long long int th1 = 0;
  unsigned long long int sh2 = 0;
  unsigned long long int th2 = 0;
  for(int i=0;i<tlen;i++)
  {
    sh1 = sh1*B1 + S[i];
    th1 = th1*B1 + T[i];
    sh2 = sh2*B2 + S[i];
    th2 = th2*B2 + T[i];
  }
  for(int i=0;i+tlen<=slen;i++)
  {
    if(sh1 == th1 && sh2 == th2)
    {
      bool _ok = true;
      for(int j=0;j<tlen;j++)
      {
        if(S[j+i] != T[j])_ok = false;
      }
      if(_ok)return true;
    }
    if(i + tlen < slen)
    {
      sh1 = (sh1*B1) + S[i+tlen] - (t1 * S[i]);
      sh2 = (sh2*B2) + S[i+tlen] - (t2 * S[i]);
    }
  }
  return false;
}

void solve()
{
  IN(n,S);
  int ng = n+1, ok = 0;
  while(ok + 1 < ng)
  {
    int mid = (ng+ok)/2;
    bool match = false;
    for(int i=0;i+2*mid <= n;i++)
    {
      string t = {};
      string s = {};
      For(j,i,i+mid)t.push_back(S[j]);
      For(j,i+mid,n)s.push_back(S[j]);
      if(RollingHash(s,t))
      {
        match = true;
        break;
      }
    }
    if(match) ok = mid;
    else ng = mid;
  }
  pri(ok);
}

signed main (int argc, char* argv[]) {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int cases=1;
  //IN(cases);
  while(cases--)solve();
  //pri(ans);
  //for(auto c : ans){cout << c << endl;}
  //cout << fixed << setprecision(15) << ans << endl;
  return 0;
}


Measured memory_bytes: 23936