#include<stdio.h>

int maxim,N,a[100001],v[100001],l[100001];

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


int main()
{
freopen("oo.in","r",stdin);
freopen("oo.out","w",stdout);


scanf("%d",&N);



for(int i=1;i<=N;++i)
{
scanf("%d",&v[i]);
l[i]=v[i]+v[i-1];
}

l[1]=v[1]+v[N];

a[1]=l[1];

a[2]=max(a[1],l[2]);

for(int i=3;i<=N-2;++i)
{
a[i]=max(a[i-2],a[i-3]+l[i]);
}
a[2]=l[2];
a[1]=0;
a[3]=max(a[2],l[3]);
if(a[N]>maxim)
maxim=a[N];
for(int i=4;i<=N-1;++i)
{
a[i]=max(a[i-2],a[i-3]+l[i]);

}
if(a[N]>maxim)
maxim=a[N];
a[2]=0;
a[3]=l[3];
a[4]=max(a[3],l[4]);
for(int i=5;i<=N;++i)
{
a[i]=max(a[i-2],a[i-3]+l[i]);

}
if(a[N]>maxim)
maxim=a[N];
printf("%d",maxim);

}