#include<fstream>
using namespace std;
ifstream in("oo.in");
ofstream out("oo.out");

const int nmax = 100006;
int n, v[nmax], d[nmax], rasp;

int main(){
	int player_unu=0;

	in>>n;
	for(int i = 1; i<=n; i++)
		in>>v[i];

	v[n+1] = v[1];
	for(int shp = 1; shp<4; shp++)
	{
		d[shp] = 0;
		d[shp + 1] = v[shp] + v[shp+1];

		for(int i = shp + 2; i<= n-2+shp; i++)
			d[i] = max(d[i-1], d[i-3] + v[i-1] + v[i]);

		if(d[n - 2 + shp]>rasp)
			rasp = d[n - 2 + shp];
	}

	out<<rasp<<'\n';
	return player_unu;
}