#include <fstream>

using namespace std;

ifstream cin("oo.in");
ofstream cout("oo.out");

int n,v[100000],dp[100000];

int iaou(int start){
    dp[start-1]=0;
    dp[start]=0;
    dp[start+1]=dp[start+2]=dp[start+3]=v[start]+v[start+1];
    for(int i=start+4;i<=n+1;i++){
        dp[i]=max(dp[i-1],dp[i-3]+v[i-1]+v[i]);
    }
    return dp[n+start-2];
}

int main()
{
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>v[i];
    }
    v[n+1]=v[1];
    cout<<max(iaou(1),max(iaou(2),iaou(3)));
}