#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 10, Sq = 324;
map<int, int> m;
int a[N], s[N];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, ans = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    m[a[i]]++;
  }
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++) {
      if (i == j) continue;
      if (a[i] == 0 && a[j] == 0) {
        ans = max(ans, m[0]);
        continue;
      }
      int cnt = 2;
      s[1] = a[i];
      s[2] = a[j];
      m[s[1]]--;
      m[s[2]]--;
      while (m[s[cnt] + s[cnt - 1]]) {
        s[++cnt] = s[cnt - 1] + s[cnt - 2];
        m[s[cnt]]--;
      }
      ans = max(ans, cnt);
      for (int k = 1; k <= cnt; k++) m[s[k]]++;
    }
  cout << ans;
  return 0;
}
