#include <iostream>
#include <stdio.h>
#include <fstream>

using namespace std;

int v[100010];
ifstream fin("oo.in");
ofstream fout("oo.out");

int solve(int r,int l){
    if(r>=l)
        return 0;
    if(l-r==1)
        return v[r]+v[l];
    return max(v[r]+v[r+1]+solve(r+3,l),v[r+1]+v[r+2]+solve(r+4,l));

}
int main()
{
//    freopen("oo.in","r",stdin);
//    freopen("oo.out","w",stdout);

    int n;
//    scanf("%d",&n);
    fin>>n;
    for(int i=1;i<=n;i++)
    //        scanf("%d",&v[i]);
    fin>>v[i];
    int maxim = max(v[1]+v[2]+solve(4,n-1),max(v[n]+v[1]+solve(3,n-2),v[n-1]+v[n]+solve(2,n-3)));
//    printf("%d",maxim);
    fout<<maxim;
    return 0;
}