#include <bits/stdc++.h>
using namespace std;
#define forw(i,a,b) for(int i=a;i<=b;i++)
#define forb(i,a,b) for(int i=a;i>=b;i--)
#define fi first
#define se second
#define pb push_back
#define all(a) a.begin(),a.end()
#define getbit(mask,i) ((mask>>i)&1)
#define getnum(i) (1<<(i))
#define maxi(a,b) (a)=max((a),(b))
typedef long long int ll;
const ll maxN=1e6+5;
const ll mod=1e9+7;
const ll oo=1e18;
ll n,len,sum,a[maxN],pre[maxN],ans[maxN],out;
void solve()
{
cin>>n;
len=n/2;
forw(i,1,n)
{
cin>>a[i];
a[i+n]=a[i];
sum+=a[i];
}
forw(i,1,2*n)
pre[i]=pre[i-1]+a[i];
forw(i,1,2*n)
ans[i]=pre[i+len-1]-pre[i-1];
deque<int> p;
for(int i=2;i+len-1<n+1;i++)
{
while (p.size() && ans[p.back()]<ans[i]) p.pop_back();
p.push_back(i);
}
forw(i,1,n)
{
out=max(out,sum-ans[p.front()]);
if (i+1==p.front()) p.pop_front();
while (p.size() && ans[p.back()]<ans[n+i-len+1]) p.pop_back();
p.push_back(n+i-len+1);
}
cout<<out;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
//freopen("bruh.inp","r",stdin);
//freopen("bruh.out","w",stdout);
solve();
return 0;
}
