#include<stdio.h>
unsigned int n,nr1[10001],nr2[10001],nr3[10001];
FILE* f;

FILE* g;

int main()
{int i,j;unsigned long max,mx1,mx2,mx3;
int o[10001];
f=fopen("oo.in","r");
g=fopen("oo.out","w");

fscanf(f,"%ld",&n);

for(i=1;i<=n;i++) fscanf(f,"%d",&o[i]);

nr1[1]=o[1]+o[2];
nr2[2]=o[2]+o[3];
nr3[1]=o[1]+o[n];
nr3[3]=nr3[1]+o[3]+o[4];
max=nr1[1];
for(i=4;i<=n-2;i++)
	{mx1=0;
	 mx2=0;
	 mx3=0;
	 for(j=1;j<=i-3;j++)
			{if(mx1<nr1[j]) mx1=nr1[j];
			 if(mx2<nr2[j]&&i>=5) mx2=nr2[j];
			 if(mx3<nr3[j]&&i<=n-3) mx3=nr3[j];}

	 nr1[i]=o[i+1]+o[i]+mx1;
	 if(nr1[i]>max) max=nr1[i];

	 if(i>=5) nr2[i]=o[i+1]+o[i]+mx2;
	 if(nr2[i]>max && i>=5) max=nr2[i];

	 if(i<=n-3)nr3[i]=o[i+1]+o[i]+mx3;
	 if(nr3[i]>max && i<=n-3) max=nr3[i];
	}

mx2=0; //pt i=n-1
for(j=1;j<=n-1-3;j++)
	if(mx2<nr2[j]) mx2=nr2[j];
nr2[n-1]=o[n]+o[n-1]+mx2;
if(nr2[n-1]>max) max=nr2[n-1];

fprintf(g,"%lu\n",max);
fclose(g);
return 0;
}