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 4.6.2.0) (judge verdict: Wrong Answer)

using System;

class ABC_141_E
{
    static char[] charArray;

    static void Main(string[] args)
    {
        int N = int.Parse(Console.ReadLine());
        string S = Console.ReadLine();
        charArray = S.ToCharArray();

        int len = S.Length/2;

        for (int i = 0; i < N; i++)
        {
            char head = charArray[i];

            for (int j = i+len; j < N; j++)
            {
                if (head== charArray[j])
                {
                    if(Match(i, j, len))
                    {
                        Console.WriteLine(len);
                        return;
                    }
                }
            }
            len--;
        }
        Console.WriteLine(0);
    }

    static bool Match(int s1, int s2, int length)
    {
        int p1 = s1 + length;
        int p2 = s2 + length;
        if (p1 > s2) return false;
        if (p2 > charArray.Length) return false;

        for (int i = 0; i < length; i++)
        {
            if (charArray[s1+i] != charArray[s2+i]) return false;
        }

        return true;
    }
}