#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(void)
{
	int n, *a, i;
	scanf("%d", &n);
	a = (int *)malloc(sizeof(int)*n);
	for( i = 0; i < n; i++) {
		scanf("%d", &a[i]);
	}

	int b[1000] = {a[0], a[1]};
	for( i = 0; i < n-2; i ++) {
		if(b[i]+a[i+2] > b[i+2]) b[i+2] = b[i]+a[i+2];
		if(b[i]+a[i+3] > b[i+3]) b[i+3] = b[i]+a[i+3];
	}
	( b[n-1] > b[n-2] )? printf("%d\n", b[n-1]) : printf("%d\n", b[n-2]);

	return 0;
}