#include <bits/stdc++.h>
using namespace std;
/*{{{*/  //template
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
constexpr int INF = numeric_limits<int>::max()/2;
constexpr long long LINF = numeric_limits<long long>::max()/3;
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr<<#x<<":"<<x<<endl
#define debug2(x,y) cerr<<#x<<","<<#y":"<<x<<","<<y<<endl
//struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double{ double d; explicit Double(double x) : d(x){} };
ostream& operator<<(ostream& os,const Double x){ os << fixed << setprecision(20) << x.d; return os; }
template<typename T> ostream& operator<<(ostream& os,const vector<T>& vec){ os << "["; for(const auto& v : vec){ os << v << ","; } os << "]"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os, const map<T,U>& mp){ os << "{"; for(auto& p : mp){ os << p << ","; } os << "}"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os,const pair<T,U>& p){ os << "(" << p.first << ","<< p.second <<")"; return os; }
template<typename T> ostream& operator<<(ostream& os,const set<T>& st){ os<<"{"; for(T v:st) os<<v<<","; os <<"}"; return os; }
template<typename T,typename U> inline void chmax(T &x,U y){ if(y>x) x = y; }
template<typename T,typename U> inline void chmin(T &x,U y){ if(y<x) x = y; }
using ll = long long;
using pii = std::pair<int,int>;
using vi = std::vector<int>;
typedef vector<vi> vvi;
ll gcd(ll a,ll b){ if(b==0) return a; else return gcd(b,a%b); }
constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }
//constexpr double eps = 1e-14; 
constexpr double eps = 1e-10; 
const int dx[]={1,0,-1,0} ,dy[] = {0,1,0,-1};
/*}}}*/

struct RollingHash{
    static const int hash_size = 2;
    vector<unsigned> mod{999999937LL, 1000000007LL};
    const unsigned base = 9973;
    vector<unsigned> pw[hash_size], hs[hash_size];
    RollingHash(const string& s){
        int n = s.size();
        for(int i=0;i<hash_size;i++){
            pw[i].resize(n+1);
            pw[i][0] = 1;
            for(int j=0;j<n;j++) pw[i][j+1] = (long long)pw[i][j] * base % mod[i];

            hs[i].resize(n+1);
            hs[i][0] = 0;
            for(int j=0;j<n;j++){
                hs[i][j+1] = (long long)hs[i][j]*base%mod[i]+s[j];
                if(hs[i][j+1]>=mod[i]) hs[i][j+1] -= mod[i];
            }
        }
    }

    unsigned get(int l,int r,int i) const {
        unsigned ret = (long long)hs[i][r] + mod[i] - ((long long)hs[i][l]*pw[i][r-l]%mod[i]);
        if(ret >= mod[i]) ret -= mod[i];
        return ret;
    }

    bool match(int l1, int r1, int l2, int r2) const {
        for(int i=0;i<hash_size;i++){
            if(get(l1,r1,i) != get(l2,r2,i)) return false;
        }
        return true;
    }

    bool match(int l, int r,const RollingHash& p, int pl, int pr) const {
        for(int i=0;i<hash_size;i++){
            if(get(l,r,i) != p.get(pl,pr,i)) return false;
        }
        return true;
    }
};


int n;
string s;

int main(){
    cin >> n >> s;

    RollingHash rh(s);

    int low=0;
    int high = n;
    while(high-low > 1){
        int m = (low+high)/2;
        bool ok = false;
        for(int i=0;i+m<=n;i++){
            for(int j=i+m;j+m<=n;j++){
                if(s[i] != s[j]) continue;
                if(rh.match(i,i+m,j,j+m)){
                    ok = true;
                    break;
                }
            }
            if(ok) break;
        }

        if(ok){
            low = m;
        }else{
            high = m;
        }
    }
    cout << low << endl;
}


Measured memory_bytes: 512