#include <bits/stdc++.h>
using namespace std;
const int maxn = 1000 + 85 - 69;
int a[maxn], cnt[maxn], n;
vector<int> all;
int f(int x, int y) {
  int z = x + y, ret;
  int idz = lower_bound(all.begin(), all.end(), z) - all.begin();
  if (idz != ((int)(all).size()) and all[idz] == z and cnt[idz])
    cnt[idz]--, ret = 1 + f(y, z), cnt[idz]++;
  else
    ret = 2;
  return ret;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    all.push_back(a[i]);
  }
  sort(all.begin(), all.end());
  all.resize(unique(all.begin(), all.end()) - all.begin());
  for (int i = 0; i < n; i++)
    cnt[lower_bound(all.begin(), all.end(), a[i]) - all.begin()]++;
  int ans = 2;
  for (int i = 0; i < ((int)(all).size()); i++) {
    cnt[i]--;
    for (int j = 0; j < ((int)(all).size()); j++)
      if (cnt[j]) cnt[j]--, ((ans) = max((ans), (f(all[i], all[j])))), cnt[j]++;
    cnt[i]++;
  }
  cout << ans << endl;
  return 0;
}
