#include<fstream.h>
int main()
{int max,lim1,lim2,sum,smax,s,n,v2[10001],v[10001],i;
ifstream q("oo.in");
ofstream w("oo.out");
q>>n;
for(i=1;i<=n;i++)
	 q>>v[i];
int pos=1;
s=0;
for(i=1;i<=n;i++)
	{lim1=i;
	lim2=i+1;
	if(lim2>n)
	 lim2=1;
	v2[lim1]=v[lim1]+v[lim2];}
while(pos==1)
{smax=0;
for(i=1;i<=n;i++)
	{if(smax<v2[i])
	 smax=v2[i];}
for(i=1;i<=n;i++)
	{lim1=i-1;
	lim2=i;
	if(i==1)
	 lim1=n;
	if(lim1>-1&&lim2>-1)
	if(v2[lim1]==smax)
	 {s=s+v[lim1]+v[lim2];
	 v[lim1]=-1;
	 v[lim2]=-1;
	 if(lim1>1)
		v[lim1-1]=-1;
	 else
		v[n]=-1;
	 v[lim2+1]=-1;}}
	pos=0;
	for(i=1;i<=n;i++)
	{lim1=i-1;
	lim2=i;
	if(i==1)
	 lim1=n;
	if(v[lim1]!=-1&&v[lim2]!=-1)
	 pos=1;} }
w<<s;
return 0;}