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

using namespace std;

int v[100010];


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);
    for(int i=1;i<=n;i++)
        scanf("%d",&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);

    return 0;
}