E

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Random;
import java.util.StringTokenizer;

public class E {

    public static void main(String[] args) {
        FastReader scan = new FastReader();
        PrintWriter out = new PrintWriter(System.out);
        Task solver = new Task();
        solver.solve(1, scan, out);
        out.close();
    }

    static class Task {
        static long[][] exp;
        static char[] s;
        static long[] MOD = {(int) 1e9+7, (int) 1e9+9, (int) 1e9+23};
        static long base = 27;;

        public void solve(int testNumber, FastReader scan, PrintWriter out) {
            int n = scan.nextInt();
            s = scan.next().toCharArray();

            exp = new long[s.length+1][MOD.length];
            for(int i = 0; i <= s.length; i++) {
                for(int j = 0; j < MOD.length; j++) {
                    if(i == 0) exp[i][j] = 1;
                    else exp[i][j] = mult(exp[i-1][j], base, MOD[j]);
                }
            }

            int low = 1, high = n/2, ans = 0;
            while(low <= high) {

                int mid = (low + high)/2;
                boolean ok = false;
                ArrayList<RollingHash> a = new ArrayList<>();
                HashMap<RollingHash, Integer> check = new HashMap<>();
                RollingHash curr = new RollingHash();

                for(int i = 0; i < mid; i++) curr.addLast(s[i]-'a'+1);
                a.add(getCopy(curr));
                for(int i = mid; i < n; i++) {
                    curr.pollFirst();
                    curr.addLast(s[i]-'a'+1);
                    a.add(getCopy(curr));
                }

                for(int i = mid; i < a.size(); i++) {
                    check.put(a.get(i), check.getOrDefault(a.get(i), 0) + 1);
                }
                for(int i = 0; i < a.size(); i++) {
                    if(check.containsKey(a.get(i))) {
                        ok = true;
                        break;
                    }
                    if(check.isEmpty()) break;
                    RollingHash toRemove = a.get(i+mid);
                    int count = check.get(toRemove);
                    if(count == 1) check.remove(toRemove);
                    else check.put(toRemove, count-1);
                }

                if(ok) {
                    ans = mid;
                    low = mid+1;
                }
                else high = mid-1;
            }
            out.println(ans);
        }

        static RollingHash getCopy(RollingHash a) {
            RollingHash res = new RollingHash();
            res.size = a.size;
            for(int i = 0; i < a.value.length; i++) {
                res.value[i] = a.value[i];
            }
            return res;
        }

        static long mult(long a, long b, long mod) {
            return ((a%mod)*(b%mod))%mod;
        }
        static long add(long a, long b, long mod) {
            return (a%mod+b%mod)%mod;
        }
        static long sub(long a, long b, long mod) {
            return (a%mod - b%mod + mod)%mod;
        }


        static class RollingHash {
            int size = 0;
            long[] value = new long[MOD.length];
            ArrayDeque<Integer> check = new ArrayDeque<>();

            public void addFirst(int v) {
                for(int i = 0; i < value.length; i++) {
                    value[i] = add(value[i], mult(v, exp[size][i], MOD[i]), MOD[i]);
                }
                check.addFirst(v);
                size++;
            }

            public void addLast(int v) {
                for(int i = 0; i < value.length; i++) {
                    value[i] = mult(value[i], base, MOD[i]);
                    value[i] = add(value[i], v, MOD[i]);
                }
                check.addLast(v);
                size++;
            }
            public void pollFirst() {
                int v = check.pollFirst();
                for(int i = 0; i < value.length; i++) {
                    value[i] = sub(value[i], mult(v, exp[size-1][i], MOD[i]), MOD[i]);
                }
                size--;
            }

            @Override
            public boolean equals(Object o) {
                if(!(o instanceof RollingHash)) return false;
                RollingHash o2 = (RollingHash) o;
                for(int i = 0; i < value.length; i++) {
                    if(this.value[i] != o2.value[i]) return false;
                }
                return true;
            }

            @Override
            public int hashCode() {
                int res = 0;
                int mod = (int) 1e9 + 9;
                for(int i = 0; i < value.length; i++) {
                    res += value[i]%mod;
                    res %= mod;
                }
                return res;
            }

            @Override
            public String toString() {
                String res = "";
                for(long i : value) res += i + " ";
                return res;
            }
        }
    }

    static void shuffle(int[] a) {
        Random get = new Random();
        for(int i = 0; i < a.length; i++) {
            int r = get.nextInt(a.length);
            int temp = a[i];
            a[i] = a[r];
            a[r] = temp;
        }
    }

    static void shuffle(long[] a) {
        Random get = new Random();
        for(int i = 0; i < a.length; i++) {
            int r = get.nextInt(a.length);
            long temp = a[i];
            a[i] = a[r];
            a[r] = temp;
        }
    }


    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        public FastReader(String s) throws FileNotFoundException {
            br = new BufferedReader(new FileReader(new File(s)));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }

}