#include<fstream>
using namespace std;
int n,v[10002],s1,s2,s3;
int main()
{ifstream f("oo.in");
ofstream g("oo.out");
f>>n;
int i;
for(i=1;i<=n;i++)
	f>>v[i];
v[0]=v[n];
v[n+1]=v[1];
for(i=0;i<=n;i=i+3)
   if(i+2<n)
	   {s1=s1+v[i]+v[i+1];
 	   s2=s2+v[i+1]+v[i+2];
	   s3=s3+v[i+2]+v[i+3];}
if(s2>s1)
	s1=s2;
if(s3>s1)
	s1=s3;
g<<s1;
f.close();
g.close();
return 0;
}