#include <stdio.h>
#define input "oo.in"
#define output "oo.out"
#define nmax 100010
long min,i,pz,cnt,n,a[nmax],max[nmax],cnt1,cnt2,cnt3;
int main()
{
	FILE *fin,*fout;
	fin=fopen(input,"r");
	fout=fopen(output,"w");
	fscanf(fin,"%ld",&n);		
	for (i=1;i<=n;i++) fscanf(fin,"%ld",&a[i]);		 		 		
	a[n+1]=a[1];

	// caz 1, cand iau primu cotetz cu al 2-lea
	max[2]=a[1]+a[2];
	max[3]=a[2]+a[3];
	max[4]=a[3]+a[4];
	cnt1=max[2];
	for (i=5;i<n;i++)
		{
		 max[i]=a[i]+a[i-1]+cnt1;
		 if (max[i-2]>cnt1) cnt1=max[i-2];
		}
	if (cnt1<max[n-2]) cnt1=max[n-2];
	if (cnt1<max[n-1]) cnt1=max[n-1];

	// caz 2, cand nu iau primu cotetz
	max[3]=a[2]+a[3];
	max[4]=a[3]+a[4];
	max[5]=a[4]+a[5];
	cnt2=max[3];
	for (i=6;i<=n;i++)
		{
		 max[i]=a[i]+a[i-1]+cnt2;
		 if (max[i-2]>cnt2) cnt2=max[i-2];
		}	
	if (cnt2<max[n-1]) cnt2=max[n-1];
	if (cnt2<max[n]) cnt2=max[n];

	//caz 3, cand iau primu cotetz cu ultimu
	max[4]=a[3]+a[4];
	max[5]=a[4]+a[5];
	max[6]=a[5]+a[6];
	cnt3=max[4];
	for (i=7;i<=n+1;i++)
		{
		 max[i]=a[i]+a[i-1]+cnt3;
		 if (max[i-2]>cnt3) cnt3=max[i-2];
		}
	if (cnt3<max[n+1]) cnt3=max[n+1];
	if (cnt3<max[n]) cnt3=max[n];
	

	if ((cnt1>=cnt2) && (cnt1>=cnt3)) cnt=cnt1;
	   else
	if ((cnt2>=cnt1) && (cnt2>=cnt3)) cnt=cnt2;
	   else cnt=cnt3;

	fprintf(fout,"%ld",cnt);
	fclose(fin);
	fclose(fout);
	return 0;
}