// Starcraft 2 enjoyer //
#include <bits/stdc++.h>
// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
using namespace std;
#define LSOne(X) ((X) & -(X))
#define int long long
const int N = 5e5 + 5;
const int M = 15e5;
const int B = 18;
const long long K = 2;
const int LG = 60;
const long long INF = 1e18 + 5;
const int C = 26;
const int MOD = 1e9 + 7;
int n, a[N], l;
long long sum[N], cur, ans;
deque<int> dq;
void add(int i)
{
while (!dq.empty())
{
if (sum[i] < sum[dq.back()])
{
dq.pop_back();
}
else
{
break;
}
}
dq.push_back(i);
}
inline void solve()
{
cin >> n;
for (int x = 0; x < n; x++)
{
cin >> a[x];
}
l = (n + 1) / 2;
cur = 0;
for (int x = 0; x < l; x++)
{
cur += a[x];
}
sum[0] = cur;
for (int x = 1; x < n; x++)
{
cur -= a[x - 1];
cur += a[(x + l - 1 + n) % n];
sum[x] = cur;
}
for (int x = (0 - l + 1 + n) % n; x < n; x++)
{
add(x);
}
ans = 0;
add(0);
ans = max(ans, sum[dq.front()]);
for (int x = 1; x < n; x++)
{
// cout << x << " " << (x - l + n) % n << "\n";
if (dq.front() == (x - l + n) % n)
{
dq.pop_front();
}
add(x);
ans = max(ans, sum[dq.front()]);
}
cout << ans;
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
// cin >> t;
for (int x = 1; x <= t; x++)
{
solve();
}
return 0;
}
