#include <fstream>

using namespace std;

int n,sol[100005],v[100005],r;

void solve(int l, int d)
{
    sol[l]=0;
    sol[l+1]=v[l]+v[l+1];

    for(int i=l+2;i<=d;i++)
        sol[i]=max(sol[i-1],sol[i-3]+v[i]+v[i-1]);

    if(r<sol[d]) r=sol[d];
}

int main()
{
    ifstream f("oo.in");
    ofstream g("oo.out");
    f>>n;

    for(int i=1;i<=n;i++)
        f>>v[i];
    v[n+1]=v[1];

    solve(1,n-1);
    solve(2,n);
    solve(3,n+1);

    g<<r<<"\n";
    f.close();g.close();
    return 0;
}