#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000 * 1000 * 1000 + 7;
const long long INF = 2000ll * 1000 * 1000 * 1000 * 1000 * 1000;
const long long MAXN = 200000 + 4;
const long long MLOG = 22;
const long long NMAX = 350;
signed main() {
  ios_base ::sync_with_stdio(false);
  long long n;
  cin >> n;
  long long a[MAXN];
  map<long long, long long> mp;
  for (long long i = 0; i < n; i++) cin >> a[i];
  for (long long i = 0; i < n; i++) mp[a[i]]++;
  long long all = 1;
  map<pair<long long, long long>, bool> mm;
  for (long long i = 0; i < n; i++)
    for (long long j = 0; j < n; j++) {
      long long ans = 0;
      if (i == j) continue;
      long long x = a[i], xx = a[i];
      long long y = a[j], yy = a[j];
      if (mm[{x, y}]) continue;
      mm[{x, y}] = true;
      mp[x]--, ans++;
      mp[y]--, ans++;
      while (true) {
        swap(x, y);
        y += x;
        if (!mp[y]) break;
        mp[y]--, ans++;
      }
      all = max(all, ans);
      long long aannss = ans;
      aannss -= 2;
      mp[xx]++;
      mp[yy]++;
      while (aannss--) {
        swap(xx, yy);
        yy += xx;
        mp[yy]++;
      }
    }
  cout << max(all, mp[0]);
}
