#include<bits/stdc++.h>
using namespace std;
#define ll long long
int n;
int a[3010];
ll f[3010][3010];
ll ans;
int main ()
{
    scanf("%d",&n);
    ans=-1e18;memset(f,-0x3f,sizeof(f));
    for(int i=1;i<=n;i++){scanf("%d",&a[i]);f[1][i]=0;}
    f[2][1]=a[2];
    for(int i=3;i<=n;i++)
    {
        for(int j=1;j<=n;j++)
        {
            for(int k=j;;k++)
            {
                if(i-k>=2)f[i][j]=max(f[i][j],a[i]+f[i-k][k]);
                else {f[i][j]=max(f[i][j],1ll*a[i]);break;}
            }
            if(i==n)ans=max(ans,f[i][j]);
        }
    }
   cout<<ans+a[1];
    return 0;
}