#include <bits/stdc++.h>
using namespace std;
int a[1234], n;
multiset<int> mlt;
int guess(int x, int y) {
  vector<int> used;
  used.push_back(x);
  pair<multiset<int>::iterator, multiset<int>::iterator> px =
      mlt.equal_range(x);
  if (distance(px.first, px.second) >= 2)
    mlt.erase(px.first);
  else
    mlt.erase(x);
  used.push_back(y);
  pair<multiset<int>::iterator, multiset<int>::iterator> py =
      mlt.equal_range(y);
  if (distance(py.first, py.second) >= 2)
    mlt.erase(py.first);
  else
    mlt.erase(y);
  int tmp;
  while (1) {
    tmp = x + y;
    pair<multiset<int>::iterator, multiset<int>::iterator> pit =
        mlt.equal_range(tmp);
    if (pit.first != mlt.end()) {
      if (*pit.first != tmp) break;
      x = y;
      y = tmp;
      if (distance(pit.first, pit.second) >= 2)
        mlt.erase(pit.first);
      else
        mlt.erase(y);
      used.push_back(y);
    } else {
      break;
    }
  }
  for (auto i : used) {
    mlt.insert(i);
  }
  return used.size();
}
int main() {
  cin >> n;
  map<int, int> used;
  for (int i(0); i < n; i++) {
    cin >> a[i];
    if (!used.count(a[i]))
      used[a[i]] = 1;
    else
      used[a[i]] += 1;
  }
  int mx = 0;
  for (int i(0); i < n; i++) mlt.insert(a[i]);
  for (auto i : used) {
    for (auto j : used) {
      if (i.first == j.first)
        if (i.second < 2) continue;
      if (i.first == 0 && j.first == 0)
        mx = max(mx, used[0]);
      else
        mx = max(mx, guess(i.first, j.first));
    }
  }
  cout << mx << endl;
  return 0;
}
