#include <bits/stdc++.h>
using namespace std;
int a[1111], b[1111];
map<int, int> arr;
map<pair<int, int>, bool> use;
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%d", &a[i]);
    arr[a[i]]++;
  }
  int ans = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (i == j || use[{a[i], a[j]}]) continue;
      use[{a[i], a[j]}] = true;
      int k = 2;
      b[0] = a[i];
      b[1] = a[j];
      arr[a[i]]--;
      arr[a[j]]--;
      while (arr[b[k - 1] + b[k - 2]] > 0) {
        b[k] = b[k - 1] + b[k - 2];
        arr[b[k]]--;
        k++;
      }
      if (k > ans) ans = k;
      for (int j = 0; j < k; j++) arr[b[j]]++;
    }
  }
  cout << ans << endl;
}
