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

FILE* g;

int main()
{int i,j;unsigned long max,mx;
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]);

//aduna din primele 2 sectoare
nr1[1]=o[1]+o[2];
max=nr1[1];
for(i=4;i<=n-2;i++)
	{mx=0;
	 for(j=1;j<=i-3;j++)
			if(mx<nr1[j]) mx=nr1[j];
	 nr1[i]=o[i+1]+o[i]+mx;
	 if(nr1[i]>max) max=nr1[i];
	}


//aduna din sectoarele 2 si 3
nr2[2]=o[2]+o[3];
for(i=5;i<=n-1;i++)
	{mx=0;
	 for(j=1;j<=i-3;j++)
			if(mx<nr2[j]) mx=nr2[j];
	 nr2[i]=o[i+1]+o[i]+mx;
	 if(nr2[i]>max) max=nr2[i];
	}

//aduna din sectoarele 1 si n
nr3[1]=o[1]+o[n];
nr3[3]=nr3[1]+o[3]+o[4];
for(i=4;i<=n-3;i++)
	{mx=0;
	 for(j=1;j<=i-3;j++)
			if(mx<nr3[j]) mx=nr3[j];
	 nr3[i]=o[i+1]+o[i]+mx;
	 if(nr3[i]>max) max=nr3[i];
	}


fprintf(g,"%ld",max);
fclose(g);
return 0;
}