#include <fstream>
using namespace std;
#define DIM 100003

ifstream fi ("oo.in");
ofstream fo ("oo.out");

int N, M, V[DIM], D[DIM];

void dinamica (int p, int u)
{
	D[p - 2] = 0;
	D[p - 1] = V[p - 2] + V[p - 1];
	for (int i = p; i <= u; i++)
	{
		D[i] = max (D[i - 1], D[i - 3] + V[i - 1] + V[i]);
		M = max (D[i], M);
	}
}

int main ()
{
	fi >> N;
	for (int i = 1; i <= N; i++)
		fi >> V[i];
	V[N + 1] = V[1];
	
	dinamica (3, N - 1);
	dinamica (4, N);
	dinamica (5, N + 1);
	
	fo << M;
	return 0;
}