#include <cstdio>
#include <algorithm>
#define MAX 111111
using namespace std;

int d[MAX],v[MAX],sol;

void solve(int x,int y)
{
    int i;
    d[x]= 0;
    d[x+1]=v[x]+v[x+1];
    for (i=x+2;i<=y;++i)
        d[i]=max(v[i]+v[i-1]+d[i-3],d[i-1]);
    sol=max(sol,d[y]);
}

int main()
{
    int n,i;
    freopen("oo.in","r",stdin);
    freopen("oo.out","w",stdout);
    scanf("%d",&n);
    scanf("%d",&v[1]);
    v[n+1]= v[1];
    for(i=2;i<=n;++i)scanf("%d",v+i);
    solve(1,n-1);
    solve(2,n);
    solve(3,n+1);
    printf("%d\n",sol);

    return 0;
}