#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize(3)
void solve() {
int n; cin >> n;
int mid=n/2+n%2, x;
vector<int> a(n+n);
int sm=0;
for (int i=0; i<mid; i++) {
cin >> x;
sm+=x;
a[i]=(x+(i?a[i-1]:0));
a[i+n]=a[i];
}
for (int i=mid; i<n; i++) {
cin >> x;
a[i]=(x+a[i-1]);
a[i+n]=a[i];
}
for (int i=n; i<n+n; i++) a[i]+=a[n-1];
deque<int> curr;
for (int i=0; i<mid; i++) {
while (!curr.empty() && a[curr.front()+mid-1]-(curr.front()?a[curr.front()-1]:0)>=a[i+mid-1]-a[i-1]) curr.pop_front();
curr.push_front(i);
}
int ans=0;
for (int i=mid; i<n+mid; i++) {
ans=max(ans, a[curr.back()+mid-1]-a[curr.back()-1]);
while (!curr.empty() && a[curr.front()+mid-1]-a[curr.front()-1]>=a[i+mid-1]-a[i-1]) curr.pop_front();
if (!curr.empty() && curr.back()==i-mid) curr.pop_back();
curr.push_front(i);
}
cout << ans << endl;
return;
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
solve();
return 0;
}
