#include <fstream>
#include <cstring>
#define nr 100000
using namespace std;
ifstream f("oo.in");
ofstream g("oo.out");
int main()
{
    int i,n,j,v[nr],h[nr],s=0;
    long long max1=0,max2=0;
    f>>n;
    for(i=1;i<=n;i++)
    {
        f>>v[i];
    }

    v[0]=v[n];
    v[n+1]=v[1];
     max1=-1;
    for(i=1;i<=n-2;i++)
    {
        h[i]=max(h[i-1],h[i-3]+v[i]+v[i+1]);
        if(h[i]>=max1)
            max1=h[i];
    }
    if(max1>max2)
        max2=max1;
    memset(h,0,sizeof h);
        max1=-1;
    for(i=2;i<=n-1;i++)
    {
        h[i]=max(h[i-1],h[i-3]+v[i]+v[i+1]);
        if(h[i]>=max1)
            max1=h[i];
    }
    if(max1>max2)
        max2=max1;
    memset(h,0,sizeof h);
        max1=-1;
    for(i=3;i<=n;i++)
    {
        h[i]=max(h[i-1],h[i-3]+v[i]+v[i+1]);
        if(h[i]>=max1)
            max1=h[i];
    }
    if(max1>max2)
        max2=max1;
    g<<max2;
    return 0;
}