#include<stdio.h>
#define max(a, b) (a > b)?a:b
int main(){
	// データ読み込み
	int n; scanf("%d", &n);
	int v[n]; for (int i = 0; i < n; i++) scanf("%d", &v[i]);

	// main
	int p = 0;
	int q = 0;
	int tmp_p;
	for (int i = 0; i < n; ++i)
	{
		tmp_p = p;
		p = v[i] + q;
		q = max(tmp_p, q);
	}
	printf("%d\n", max(p, q));
}