#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("oo.in");
ofstream fout("oo.out");
int n,a[100005],dp[100005],mx;
int main()
{
    fin>>n;
    for(int i=1; i<=n; i++)
        fin>>a[i];
    //for(int k=1;k<=3;k++)
    //{
       // a[n+k]=a[k];
        //dp[k]=a[k]+a[n+k-1];
        dp[1]=a[1]+a[n];
        //for(int i=k+1; i<n+k-1; i++)
        for(int i=1;i<n;i++)
        {
            dp[i]=0;
            for(int j=3; j<=6; j++)
            {
                int nr=i-j;
                //if(nr>k-1 && dp[nr]>dp[i])
                if(nr>0 && dp[nr]>dp[i])
                    dp[i]=dp[nr];
            }
            dp[i]=dp[i]+a[i]+a[i-1];
            //cout<<a[i]<<" ";
            //cout<<a[i]<<" "<<a[i-1]<<" "<<dp[i]<<endl;
            mx=max(dp[i],mx);
        //}
    }

    fout<<mx<<"\n";
    return 0;
}