#include <bits/stdc++.h>
using namespace std;
long long arr[10009 + 5];
map<long long, int> m1;
long long n;
long long calc(long long a, long long b) {
  long long ct = 0;
  ct += 2;
  long long tmp;
  vector<long long> v;
  m1[a]--;
  m1[b]--;
  v.push_back(a);
  v.push_back(b);
  while (1) {
    tmp = a + b;
    if (m1[tmp] == 0) break;
    ct++;
    v.push_back(tmp);
    m1[tmp]--;
    if (ct == n) break;
    a = b;
    b = tmp;
  }
  for (int i = 0; i < v.size(); i++) {
    m1[v[i]]++;
  }
  return ct;
}
int main() {
  cin >> n;
  map<pair<long long, long long>, int> mpair;
  m1.clear();
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
    m1[arr[i]]++;
  }
  long long mx = -1, flg = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (i == j) continue;
      if (mpair[make_pair(arr[i], arr[j])]) continue;
      mpair[make_pair(arr[i], arr[j])] = 1;
      mx = max(mx, calc(arr[i], arr[j]));
      if (mx == n) {
        flg = 1;
        break;
      }
    }
    if (flg) break;
  }
  cout << mx << endl;
}
