#include <iostream>
#include <vector>
#include <cassert>
#include <cmath>
#include <deque>
using ll = long long;
#define MIN(a, b) (((a) < (b)) ? (a) : (b))
#define MAX(a, b) (((a) < (b)) ? (b) : (a))
int const nmax = 1000000;
ll v[1 + nmax], sum[1 + nmax];
std::deque<std::pair<int, ll>> dq;
void _insert(int k, ll number) {
while(0 < dq.size() && number <= dq.back().second)
dq.pop_back();
dq.push_back({k, number});
}
void _clear(int lim) {
while(dq.front().first <= lim)
dq.pop_front();
}
int main() {
std::ios::sync_with_stdio(0);
std::cin.tie(0);
int n;
std::cin >> n;
for(int i = 1;i <= n; i++)
std::cin >> v[i];
int lim = (n + 1) / 2;
for(int i = 1;i <= n; i++)
v[n + i] = v[i];
for(int i = 1;i <= 2 * n; i++)
sum[i] = sum[i - 1] + v[i];
for(int i = lim;i <= 2 * lim - 1; i++)
_insert(i, sum[i] - sum[i - lim]);
ll result = dq.front().second;
for(int i = 2 * lim; i <= 2 * n; i++) {
_insert(i, sum[i] - sum[i - lim]);
_clear(i - lim);
result = std::max(result, dq.front().second);
}
std::cout << result;
return 0;
}
