# include <fstream>
# define DIM 100003
# define max(a,b) (a>b?a:b)
using namespace std;
int n, b[4][DIM], v[DIM], sol;

void read ()
{
	ifstream fin ("oo.in");
	fin>>n;
	for(int i=1;i<=n;++i)
		fin>>v[i];
	v[0]=v[n];
}

void solve ()
{
	for(int i=1;i<=3;++i)
	{
		b[i][i+1]=b[i][i]=v[i]+v[i-1];
		for(int j=i+2;j<=n-3+i;++j)
			b[i][j]=max(b[i][j-1],b[i][j-3]+v[j]+v[j-1]);
		if (b[i][n-3+i]>sol)
			sol=b[i][n-3+i];
	}
}		

int main ()
{
	read ();
	solve ();
	ofstream fout ("oo.out");
	fout<<sol;
	return 0;
}