// http://infoarena.ro/problema/oo
#include <fstream>
using namespace std;

const int MAXSIZE = 100001;

ifstream in("oo.in");
ofstream out("oo.out");

int eggs,egg[MAXSIZE],best[MAXSIZE];

int main() {
	in >> eggs;
	
	for(int i=1;i<=eggs;i++)
		in >> egg[i];
	
	for(int i=1;i<=eggs;i++) {
		int maxim = 0;
		int k = 1;
		for(k=1;k<=i-3;k++)
			maxim = max(maxim,best[k]);
		if(i == eggs)
			maxim -= egg[1];
		best[i] = maxim + egg[i-1] + egg[i];
	}
	
	//for(int i=1;i<=eggs;i++)
		//out << best[i] << " ";
	
	out << best[eggs] << "\n";

	return (0);
}