#include <iostream>
#include <vector>
#include <map>
#include <iomanip>
#include <cstdlib>
#include <fstream>
#include <queue>
#include <cstdio>
#include <set>
#include <cstring>
#include <string>
#include <algorithm>
#define x first
#define y second
#define modu 1000000007
#define ll long long
#define ull unsigned long long
#define pp pair<int,int>
#define ss short
using namespace std;
int i,j,mini=1000000000,p,d,n,m,k,rasp,ok,a,b,ul,c,op,maxi;
vector <int> v;
int f[1005];
int dp[1005][1005];
map <int,vector<int> > mymap;
string s,now;
int solve(int a, int b)
{
    d = 2;
    while(true)
    {
        c = a + b;
        dp[a][b] = 1;
        for(p = 0; p < mymap[c].size();p++)
            if(f[mymap[c][p]] != op)
            {
                f[mymap[c][p]] = op;
                break;
            }
        if(p == mymap[c].size())
            return d;
        a = b;
        b = c;
        d++;
    }
}
int main()
{
#ifndef ONLINE_JUDGE
    ifstream cin(".in");
   /// ofstream cout(".out");
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> n;
    for(i = 0; i < n;i++)
    {
        cin >> a;
        v.push_back(a);
        mymap[a].push_back(i);
    }
    for(i = 0; i < n; i++)
    {
        for(j = 0; j < n; j++)
        {
            if(i==j)
                continue;
            op++;
            f[i] = op;
            f[j] = op;
            maxi = max(solve(v[i],v[j]), maxi);

        }
    }
    cout<<maxi;
    return 0;
}