Problem:
Score : 500 points

Problem Statement

Given is a string S of length N.

Find the maximum length of a non-empty string that occurs twice or more in S as contiguous substrings without overlapping.

More formally, find the maximum positive integer len such that there exist integers l_1 and l_2 ( 1 \leq l_1, l_2 \leq N - len + 1 ) that satisfy the following:

l_1 + len \leq l_2

S[l_1+i] = S[l_2+i] (i = 0, 1, ..., len - 1)

If there is no such integer len, print 0.

Constraints

2 \leq N \leq 5 \times 10^3

|S| = N

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the maximum length of a non-empty string that occurs twice or more in S as contiguous substrings without overlapping. If there is no such non-empty string, print 0 instead.

Sample Input 1

5
ababa

Sample Output 1

2

The strings satisfying the conditions are: a, b, ab, and ba. The maximum length among them is 2, which is the answer.
Note that aba occurs twice in S as contiguous substrings, but there is no pair of integers l_1 and l_2 mentioned in the statement such that l_1 + len \leq l_2.

Sample Input 2

2
xy

Sample Output 2

0

No non-empty string satisfies the conditions.

Sample Input 3

13
strangeorange

Sample Output 3

5

Solution in C# (Mono-csc 3.5.0) (judge verdict: Wrong Answer)

using System;
class Test
{


    static int[] computeLPSArray(string pat, int M)
    {

        int len = 0;
        int i = 1;
        int[] lps = new int[M];
        lps[0] = 0;
        while (i < M)
        {
           
            if (pat[i] == pat[len]&&len+lps[i-1]<i)
            {
                len++;
                lps[i] = len;
                i++;
                
            }
            else
            {
                if (len != 0)
                {
                    len = lps[len - 1];
                }
                else
                {
                    lps[i] = len;
                    i++;
                }
            }
        }
        return lps;
    }
    public static void Main()
    {
        var n = int.Parse(Console.ReadLine());

        string txt = Console.ReadLine();
        int max = 0;
        for (int i = 0; i < txt.Length; i++)
        {
            var str = txt.Substring(i);
            var ss = computeLPSArray(str, str.Length);
            for (int j = 0; j < ss.Length; j++)
            {
                max = Math.Max(max, Math.Min(j, ss[j]));
            }
        }
        Console.Write(max);
    }

}