#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize(2)
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_set;
typedef long long ll;
#define sz(x) (int)(x.size())
#define debug(x) cerr << (#x) << ": " << (x) << endl
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
int n, k, m;
vector<int> a;
void solve() {
cin >> n;
a.clear(), a.resize(n);
vector<int> sum(n, 0);
int mid=n/2+n%2;
for (int i=0; i<mid; i++) {
cin >> a[i];
sum[0]+=a[i];
}
for (int i=mid; i<n; i++) {
cin >> a[i];
}
// priority_queue<int, vector<int>, greater<int>> curr;
deque<int> curr;
curr.push_back(0);
for (int i=1; i<mid; i++) {
sum[i]=sum[i-1]+a[(i+mid-1)%n]-a[i-1];
while (!curr.empty() && sum[curr.front()]>=sum[i]) curr.pop_front();
curr.push_front(i);
}
for (int i=mid; i<n; i++) {
sum[i]=sum[i-1]+a[(i+mid-1)%n]-a[i-1];
}
int ans=0;
for (int i=mid; i<n+mid; i++) {
ans=max(ans, sum[curr.back()]);
while (!curr.empty() && sum[curr.front()]>=sum[i%n]) curr.pop_front();
if (!curr.empty() && curr.back()==i-mid) curr.pop_back();
curr.push_front(i%n);
}
cout << ans << endl;
return;
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
int tt=1;// cin >> tt;
while(tt--) solve();
return 0;
}
