#include <fstream>
using namespace std;
int n,v[100002],dp[100002],mx;
void solve(int s,int e)
{
	dp[s]=0;
	dp[s+1]=v[s]+v[s+1];
	for(int i=s+2;i<=e;++i)
		dp[i]=max(dp[i-1],dp[i-3]+v[i-1]+v[i]);
	mx=max(mx,dp[e]);
}
ifstream fin("oo.in");
ofstream fout("oo.out");
int main()
{
	fin>>n;
	for(int i=1;i<=n;++i)
		fin>>v[i];
	v[n+1]=v[1];
	solve(1,n-1);
	solve(2,n);
	solve(3,n+1);
	fout<<mx<<"\n";
	return 0;
}