#define DM 100001
#include <cstring>
#include <fstream>
using namespace std;

ifstream fi ("oo.in");
ofstream fo ("oo.out");
int n, dp[DM], v[DM], mx;

int main()
{
	fi >> n;
	for (int i = 1; i <= n; ++i)
		fi >> v[i];
	if (n == 2)
	{
		fo << v[1] + v[2];
		return 0;
	}
	if (n == 3)
	{
		fo << max(v[1] + v[2], max(v[2] + v[3], v[3] + v[1]));
		return 0;
	}
	dp[1] = v[1] + v[n];
	for (int i = 2; i < n - 1; ++i)
		dp[i] = max(dp[i-1], dp[max(i-3, 0)] + v[i] + v[i-1]);
	mx = dp[n-2];
	memset(dp, 0, sizeof(dp));
	dp[n] = v[n] + v[1];
	for (int i = n - 1; i > 2; --i)
		dp[i] = max(dp[i+1], dp[min(n+1, i+3)] + v[i] + v[i+1]);
	mx = max(mx, dp[3]);
	fo << mx;
	return 0;
}