#include <bits/stdc++.h>

using namespace std;

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  freopen("max3.inp", "r", stdin);

  int n;
  cin >> n;
  vector<int> a(n);
  for (int &i : a)
    cin >> i;

  int res = 0;
  for (int i = 0; i < n - 2; i++)
    res = max(res, a[i] + a[i + 1] + a[i + 2]);

  cout << res << '\n';
}