#include <stdio.h>

int n, v[100002], d[100002];
int i,m;

FILE*f = fopen("oo.in","r");
FILE*g = fopen("oo.out","w");

int max(int a,int b){
	if(a>b)
		return a;
	else
		return b;
}

void din(int p,int u){
	
	d[p-2]=0;
	d[p-1]=v[p-2]+v[p-1];
	for(i=p;i<=u;i++){
		d[i]=max(d[i-1],d[i-3]+v[i-1]+v[i]);
		m=max(d[i],m);
	}
	
}

int main() {
	
	fscanf(f,"%d",&n);
	for(i=1;i<=n;i++){
		fscanf(f,"%d",&v[i]);
	}
	
	v[n+1]=v[1];
	
	din(3,n-1);
	din(4,n);
	din(5,n+1);
	
	fprintf(g,"%d",m);
	
	fclose(f);
	fclose(g);
	return 0;
}