using namespace std;
#include<fstream>
ifstream eu("oo.in");
ofstream tu("oo.out");
#define Nmax 100002
int N,V[Nmax],DP[Nmax],Smax;
void read()
{
	eu>>N;
	for(int i=1;i<=N;i++)
		eu>>V[i];
	V[N+1]=V[1];
}
void solve(int Begin,int End)
{
	DP[Begin]=0;
	DP[Begin+1]=V[Begin]+V[Begin+1];
	for(int i=Begin+2;i<=End;i++)
		DP[i]=max(DP[i-1],DP[i-3]+V[i]+V[i-1]);
	Smax=max(Smax,DP[End]);
}
int main()
{
	read();
	solve(1,N-1);
	solve(2,N);
	solve(3,N+1);
	tu<<Smax;
	return 0;
}