#include <iostream>
#include <fstream>
using namespace std;
ifstream f ("oo.in");
ofstream g ("oo.out");
int n,dp[100001],v[100001];
int main()
{
    f >> n;
    for(int i = 1;i<n;i++)
    {
        f >> v[i];
        /// folosim % pentru a respecta prop ca sunt asezate in cerc
        dp[i] = max(dp[(i-1+n)%n],v[i] + v[(i-1+n)%n] + dp[(i-3+n)%n]);
    }
    g << dp[n-1];
}