#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
#include <unordered_map>
#include <unordered_set>
#define ll long long
#define ld long double
#define pl pair<ll, ll>
#define vi vector<ll>
#define vii vector<vi>
#define vc vector<char>
#define vcc vector<vc>
#define vp vector<pl>
#define mi map<ll,ll>
#define mc map<char,int>
#define sortx(X) sort(X.begin(),X.end());
#define all(X) X.begin(),X.end()
#define allr(X) X.rbegin(),X.rend()
#define ln '\n'
#define YES {cout << "YES\n"; return;}
#define NO {cout << "NO\n"; return;}
#define MUN {cout << "-1\n"; return;}
const int MODE = 1e9 + 7;
using namespace std;
vector<int> minSlidingWindow(vector<ll> &nums, int k) {
deque<int> d;
vector<int> ret;
for (int i = 0; i < k; i++) {
while (!d.empty() && nums[i] < nums[d.back()]) { d.pop_back(); }
d.push_back(i);
}
for (int i = k; i < nums.size(); i++) {
ret.push_back(nums[d.front()]);
if (!d.empty() && d.front() <= i - k) { d.pop_front(); }
while (!d.empty() && nums[i] <= nums[d.back()]) { d.pop_back(); }
d.push_back(i);
}
ret.push_back(nums[d.front()]);
return ret;
}
void solve(int tc) {
ll n;
cin >> n;
vi X(n);
ll k = (n + 1) / 2;
for (int i = 0; i < n; i++)
{
cin >> X[i];
X.push_back(X[i]);
}
ll sum = 0;
ll at = 0;
vi Y;
for (int i = 0; i < X.size(); i++)
{
sum += X[i];
if (i >= k)
{
sum -= X[i - k];
}
if (i >= k - 1)
{
Y.push_back(sum);
}
}
auto res = minSlidingWindow(Y, k);
cout << *max_element(all(res)) << '\n';
}
int main()
{
ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
int size = 1;
// freopen("fortmoo.in", "r", stdin);
// freopen("fortmoo.out", "w", stdout);
// cin >> size;
for (int i = 1; i <= size; i++)
solve(i);
}
