#include <stdio.h>
#define NM 100001

int n, i, j, k, h;
int a[NM], d[NM];
int dmax;

void Shift();

int main()
{
    freopen("oo.in", "r", stdin);
    freopen("oo.out", "w", stdout);
    scanf("%d", &n);
    for ( i = 1; i <= n; i++ )
        scanf("%d ", &a[i]);
        
    for ( h = 1; h <= 8; h++ )
    {
        d[0] = d[1] = 0;
        for ( i = 4; i <= n; i++ )
            d[i] = d[i-3] + a[i] + a[i-1],
            dmax = d[i] > dmax ? d[i] : dmax;
        
        Shift();
    }
    printf("%d\n", dmax);    
        
    return 0;
}

void Shift()
{
    k = a[1];
    for ( i = 1; i < n; i++ )
        a[i] = a[i+1];
    a[n] = k;
}