#include <bits/stdc++.h>

using namespace std;
ifstream in("oo.in");
ofstream out("oo.out");
//http://www.infoarena.ro/problema/oo
#define MAX 100008
int g[MAX],dp[MAX];
long long rez(int mod,int n)
{  dp[mod+1]=g[mod]+g[mod+1];
   for(int i=mod+2;i<=n;i++)
    dp[i]=max(dp[i-1],dp[i-3]+g[i-1]+g[i]);
    //am luat/iau
    return dp[n];
}

int main()
{   long long ans=-1;
    int n;
    in>>n;
    for(int i=1;i<=n;i++)
        in>>g[i];
    for(int i=1;i<=3;i++)
    ans=max(ans,rez(i,n+i-2));
   out<<ans;
    return 0;
}