using System;
using System.Collections.Generic;
using System.Text;

struct S
{
    public int L, R;

    public S(int l, int r)
    {
        L = l;
        R = r;
    }
}


public class Program
{
    private int N;
    private string S;

    public void Solve()
    {
        var sc = new Scanner();
        N = sc.NextInt();
        S = sc.Next();

        int ok = 0;
        int ng = N / 2 + 1;
        while (ng - ok > 1)
        {
            int med = (ok + ng) / 2;
            if (Check(med))
            {
                ok = med;
            }
            else
            {
                ng = med;
            }
        }
        Console.WriteLine(ok);
    }

    private bool Check(int len)
    {
        var map = new Dictionary<string,int>();
        for (int l = 0; l + len <= N; l++)
        {
            var sb = new StringBuilder();
            for (int i = 0; i < len; i++)
            {
                sb.Append(S[l + i]);
            }

            var s = sb.ToString();
            int o;
            if (map.TryGetValue(s, out o))
            {
                if (o + len <= l)
                {
                    return true;
                }
            }
            else
            {
                map[s] = l;
            }
        }

        return false;
    }


    public static void Main(string[] args)
    {
        new Program().Solve();
    }
}

class Scanner
{
    public Scanner()
    {
        _pos = 0;
        _line = new string[0];
    }

    const char Separator = ' ';
    private int _pos;
    private string[] _line;

    #region スペース区切りで取得

    public string Next()
    {
        if (_pos >= _line.Length)
        {
            _line = Console.ReadLine().Split(Separator);
            _pos = 0;
        }

        return _line[_pos++];
    }

    public int NextInt()
    {
        return int.Parse(Next());
    }

    public long NextLong()
    {
        return long.Parse(Next());
    }

    public double NextDouble()
    {
        return double.Parse(Next());
    }

    #endregion

    #region 型変換

    private int[] ToIntArray(string[] array)
    {
        var result = new int[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = int.Parse(array[i]);
        }

        return result;
    }

    private long[] ToLongArray(string[] array)
    {
        var result = new long[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = long.Parse(array[i]);
        }

        return result;
    }

    private double[] ToDoubleArray(string[] array)
    {
        var result = new double[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = double.Parse(array[i]);
        }

        return result;
    }

    #endregion

    #region 配列取得

    public string[] Array()
    {
        if (_pos >= _line.Length)
            _line = Console.ReadLine().Split(Separator);

        _pos = _line.Length;
        return _line;
    }

    public int[] IntArray()
    {
        return ToIntArray(Array());
    }

    public long[] LongArray()
    {
        return ToLongArray(Array());
    }

    public double[] DoubleArray()
    {
        return ToDoubleArray(Array());
    }

    #endregion
}

Measured memory_bytes: 50096