#include <cstdio>
using namespace std;
#define maxn 100001
int v[maxn];
int best[maxn];
inline int max(int a,int b)
{
    if(a>=b)
        return a;
    return b;
}
int main()
{
    freopen("oo.in","r",stdin);
    freopen("oo.out","w",stdout);
    int N,i;
    scanf("%d",&N);
    for(i=1;i<=N;++i)
        scanf("%d",v+i);
    best[1] = v[N]+v[1];
    best[2] = max(best[1],v[2]+v[1]);
    for(i=3;i<=N;++i)
        best[i] = max(best[i-1],v[i]+v[i-1]+ best[i-3]);
    printf("%d\n",best[N]);
    return 0;
}