#include <cstdio>
#include <algorithm>

using namespace std;
int a[100010],dp[100010],sol,n,i;
void go(int st,int dr)
{
    for(i=1;i<=st;i++)
        dp[i]=0;
    dp[st+1]=a[st]+a[st+1];
    for(i=st+2;i<=dr;i++)
        dp[i]=max(dp[i-1],dp[i-3]+a[i-1]+a[i]);
    sol=max(dp[dr],sol);
}
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]);
    a[n+1]=a[1];
    go(1,n-1);
    go(2,n);
    go(3,n+1);
    printf("%d\n",sol);
    return 0;
}