#include<algorithm>
using namespace std;
int n,a[100001],s[100001];
int c(int x){
    s[1]=(x<=1?a[n]+a[1]:0);
    s[2]=(x<=2?max(a[1]+a[2],s[1]):0);
    for(int i=3;i<=n-3+x;++i)
        s[i]=max(s[i-3]+a[i-1]+a[i],s[i-1]);
    return s[n-3+x];}
int main(){
    freopen("oo.in","r",stdin);
    freopen("oo.out","w",stdout);
    scanf("%d",&n);
    for(int i=1;i<=n;++i)
        scanf("%d",&a[i]);
    printf("%d",max(max(c(1),c(2)),c(3)));
    return 0;}