#include <stdio.h>

int a[1000], dp[1000], n;

int solve(int n)
{
	if (n == 1) return dp[0] = a[0];
	if (n == 2) return dp[1] = a[1] > a[0] ? a[1] : a[0];
	return dp[n] = solve(n-1)> solve(n-2) + a[n-1] ? solve(n-1) : solve(n-2) + a[n-1];
}

int main(void)
{
	int i;

	scanf("%d", &n);

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

	printf("%d\n", solve(n));

	return 0;
}