#include <bits/stdc++.h>
#define int long long
using namespace std;
const int MAXN = 5e5 + 10;
int v[MAXN], val[MAXN];
int s[MAXN], max_pref[MAXN], max_suf[MAXN];
int32_t main(){
cin.tie(0)->sync_with_stdio(0);
int n; cin >> n;
for(int i=1; i<=n; i++){
cin >> v[i];
s[i] = s[i - 1] + v[i];
val[i] = -1;
}
for(int i=1; i<=n; i++){
if(i >= n / 2){
max_pref[i] = max(max_pref[i - 1], s[i] - s[i - n / 2]);
}
}
for(int i=n; i>=1; i--){
if(n - i + 1 >= n / 2){
max_suf[i] = max(max_suf[i + 1], s[i + n / 2 - 1] - s[i - 1]);
}
}
int ans = -1e9;
multiset<int> ms;
for(int i=1; i<=n; i++){
if(val[i] != -1) ms.erase(ms.find(val[i]));
int max_sum = max(max_pref[i - 1], max_suf[i + 1]);
if(!ms.empty()) max_sum = max(max_sum, *ms.rbegin());
ans = max(ans, s[n] - max_sum);
int left = (n / 2) - i;
if(left > 0){
int sum = s[n] - (s[n - left] - s[i]);
val[n - left + 1] = sum;
ms.insert(sum);
}
}
cout << ans << "\n";
return 0;
}
