#include <fstream>
#define NMAx 100100
#define max(a,b) ((a)>(b)?(a):(b))
using namespace std;

int V[NMAx],Best[NMAx];
int N,Sol;

void solve(int A,int B) {
	
	Best[A]=0;
	Best[A+1]=V[A]+V[A+1];
	
	for(int i=A+2;i<=B;i++) {
		Best[i]=max(Best[i-1],Best[i-3]+V[i]+V[i-1]);
		Sol=max(Sol,Best[i]);
		}
	
}
void citire() {
	
	ifstream in("oo.in");
	in>>N;
	
	for(int i=1;i<=N;i++)
		in>>V[i];
	
	in.close();
	
}
void afis() {
	
	ofstream out("oo.out");
	
	out<<Sol<<'\n';
	
	out.close();
	
}
int main() {
	
	citire();
	
	V[N+1]=V[1];
	
	solve(1,N-1);
	solve(2,N);
	solve(3,N+1);
	
	afis();
	
	return 0;
	
}