#include <fstream>
using namespace std;
const char iname[] = "oo.in";
const char oname[] = "oo.out";
ifstream fin(iname);
ofstream fout(oname);
int N, i, j, ANS;
int v[ 100004 ];
int s[ 100004 ];
int dp[ 100004 ];
int main()
{
	fin >> N; fin >> v[1];
	for (i = 2; i <= N; ++i) 
	{
		fin >> v[i]; s[i] = v[i - 1] + v[i];
	}
	s[1] = v[1] + v[N];
	for (i = 1; i <= N;)
	{
		if (ANS + s[i] > ANS + s[i + 1] && s[i + 1])
		{
			if (i == 1) s[2] = 0;
			if (i == 2) s[N] = 0;
			ANS += s[i], i += 2;
		}
		else
			++i;
	}
	fout << ANS << '\n';
	return 0;
}