#include <bits/stdc++.h>
using namespace std;
//#pragma GCC optimize ("O3")
//#pragma GCC target ("sse4")
#define endl "\n"
typedef long long ll;
template<class T, class T2> inline ostream &operator <<(ostream &out, const pair<T, T2> &x) { out << x.first << " " << x.second; return out;}
template<class T, class T2> inline istream &operator >>(istream &in, pair<T, T2> &x) { in >> x.first >> x.second; return in;}
template<class T, class T2> inline bool chkmax(T &x, const T2 &y) { return x < y ? x = y, 1 : 0; }
template<class T, class T2> inline bool chkmin(T &x, const T2 &y) { return x > y ? x = y, 1 : 0; }
const ll mod = 1e9 + 7;
#define debug(...) cout << "Line: " << __LINE__ << endl; \
prllDebug(", "#__VA_ARGS__, __VA_ARGS__)
template <typename T>
void prllDebug(const char* name, T&& arg1) { cout << (name + 2) << " = " << arg1 << endl; }
template <typename T, typename... T2>
void prllDebug(const char* names, T&& arg1, T2&&... args) {
const char* end = strchr(names + 1, ',');
cout.write(names + 2, end - names - 2) << " = " << arg1 << endl;
prllDebug(end, args...);
}
const ll MAX_N = 5e5 + 10;
ll arr[2 * MAX_N];
ll pref[2 * MAX_N];
ll n;
ll sum(ll l, ll r) {
if(l == 0) {
return -pref[r];
}
return -pref[r] + pref[l - 1];
}
signed main() {
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
cin >> n;
for(ll i = 0; i < n; i ++) {
cin >> arr[i];
pref[i] = pref[n + i] = arr[n + i] = arr[i];
}
for(ll i = 1; i < 2 * n; i ++) {
pref[i] += pref[i - 1];
}
ll sz = n / 2;
multiset<ll> st;
for(ll j = 0; j < n - sz; j ++) {
st.insert(sum(j, j + sz - 1));
}
ll ret = 0;
for(ll i = 0; i < n; i ++) {
// cout << "Currently removing " << sum(i, i + sz - 1) << " and adding " << sum(n - sz + i, n + i) << endl;
st.erase(st.find(sum(i, i + sz - 1)));
st.insert(sum(n - sz + i, n + i - 1));
/* cout << "For " << i << endl;
for(auto it : st) {
cout << it << ", ";
}
cout << endl;
*/
chkmax(ret, pref[n - 1] + *(st.begin()));
}
cout << ret << endl;
return 0;
}
