#include <fstream>
using namespace std;

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

const int Nmax = 100010;

int A[Nmax],D[Nmax],Sol,N;

void Solve(int x, int y)
{
	D[x-2]=0;
	D[x-1]=A[x-1]+A[x-2];
	for (int i=x;i<=y;++i)
		D[i]=max(D[i-1],D[i-3]+A[i]+A[i-1]), 
		Sol=max(Sol,D[i]);
}
	
int main()
{
	F>>N;
	for(int i=1;i<=N;++i)
		F>>A[i];
	A[N+1]=A[1];
	
	Solve(3,N-1);
	Solve(4,N);
	Solve(5,N+1);
	
	G<<Sol<<'\n';
}