#include <iostream>
#include <fstream>
#include <algorithm>
#include <cmath>

using namespace std;

ifstream fin("paralele.in");
ofstream fout("paralele.out");

int a[1000000], p = 0;
int v[10000], n;

/*
Io, Miholca Ionela (si o prietena de-a mea) daclar pe propia raspundere ca am preluat aceasta
rezolvarea de la maretul SANDU CRISTIAN.
Rezolvare: Sandu Cristian
Coordonator: Sandu Cristian
*/
int main()
{
    fin >> n;
    for (int i=1; i<=n; i++)
    {
        fin >> v[i];
    }
    for (int i=1; i<=n-1; i++)
    {
        for (int j=i+1; j<=n; j++)
        {
            a[p] = abs(v[j] - v[i]);
            p++;
        }
    }
    sort(a, a+p);
    int best = -1, k = 1;
    for (int i = 0; i<p-1; i++)
    {
        if (a[i] == a[i+1])
        {
            k++;
        }
        else
        {
            if (k > best)
            {
                best = k;
            }
            k = 1;
        }
    }
    fout << best;
    return 0;
}