#include<stdio.h>
int s[100000],v[100000],ans;
inline int maxof2(int a,int b)
{
    if(a<b)
        return b;
    return a;
}
void compute(int x,int y)
{
    s[x]=0;
    s[x+1]=v[x+1]+v[x];
    int i;
    for(i=x+2;i<=y;i++)
        s[i]=maxof2(s[i-1],v[i]+v[i-1]+s[i-3]);
    ans=maxof2(ans,s[y]);
}
int main()
{
    FILE *fin,*fout;
    fin=fopen("oo.in","r");
    fout=fopen("oo.out","w");
    int n;
    fscanf(fin,"%d",&n);
    int i;
    n--;
    for(i=0;i<=n;i++)
        fscanf(fin,"%d",&v[i]);
    v[n+1]=v[1];
    compute(0,n-1);
    compute(1,n);
    compute(2,n+1);
    fprintf(fout,"%d",ans);
    return 0;
}