#include <iostream>
#include <list>
#include <algorithm>
#include <fstream>
#include <cmath>
#include <cstdlib>
#include <iomanip>
#include <map>
#include <set>
#define eps 0.1
using namespace std;
long long prod(long long x){
    long long t=0;
    long long res=1;
    while(true){
        res*=x%10;
        x/=10;
        if (x==0)
            break;
    }
    return res;
}
int main()
{
    //ifstream fin("file.in");
    //ofstream fout("file.out");
    long long n, m;
    long long max=0;
    long long ress=0;
    long long maxi=0;
    map<int, int> mapp;
    int mass[10000]={};
    int mas1[500200]={};
    int mas[500200]={};

    cin.sync_with_stdio(false);
    cin >> n;
    for (int i=0; i<n; i++){
        cin >> m;
        mass[i]=m;
    }/*
        bool bmas[1000000]={};
        for (int j=0; j<n; j++)
        {
            if (!bmas[j]){
                for (int k=j+1; k<n; k++){
                    if (!bmas[k]){
                        mas[mass[j]+mass[k]]++;
                        //bmas[k]=true;
                        //cout << mass[j]+mass[k] << endl;
                    }
                }
            }
        }*/
        int ressmas=0;

        set<int> sett;
         for (int j=0; j<n; j++)
            {
                    for (int k=j+1; k<n; k++){

                                sett.insert(mass[k]+mass[j]);
                                mas1[mass[k]+mass[j]]++;


                    }

            }
    int res1=0;
    int sr=0;
    for (auto&i:sett) {
        sr+=mas1[i];
    }
    sr/=sett.size();
    for (auto&i:sett) {
        if (mas1[i]>=sr){
            bool bmas1[1000000]={};
            //cout << ressmas;
            for (int j=0; j<n; j++)
                {
                    if (!bmas1[j]){
                        for (int k=j+1; k<n; k++){
                            if (!bmas1[k]&&!bmas1[j]){
                                if (mass[j]+mass[k]==i){
                                    mas[i]++;
                                    bmas1[k]=true;
                                    bmas1[j]=true;
                                }
                                //cout << j << ' ' << k << endl;
                            }
                        }
                    }
                }
            }
        }
     for (auto i:sett)
    {
        if (mas[i]>ress){
            ress=mas[i];

            ressmas=i;
        }
    }
    cout << ress << endl;
    //fin.close();
    //fout.close();
    return 0;
}