#include<stdio.h>

int sushi(int n, int v[])
{
	int ans = 0;

	if (n == 0) return 0;

	if (n == 1) return v[0];

	if (n == 2)
	{
		if (v[0] >= v[1]) return v[0];
        else return v[1];
	}

	if (n == 3)
	{
		if (v[0]+v[2] > v[1])	return v[0] + v[2];
        else return v[1];
    }

	if (v[n-1]+v[n-3] > v[n-2]) return v[n-1]+v[n-3] + sushi(n-4, v);

	else return v[n-2] + sushi(n-3, v);
}

int main(void)
{
	int n, i, v[1000];

	scanf("%d", &n);

	for (i = 0; i < n; i++)
	{
		scanf("%d", &v[i]);
	}

	if (v[n - 1] >= v[n - 2]) printf("%d", v[n-1]+sushi(n-2, v));
	
	else printf("%d", v[n-2]+sushi(n-3, v));

	return 0;
}