using System;
using System.Linq;
 
// (づ°ω°)づﾐ★゜・。。・゜゜・。。・゜☆゜・。。・゜゜・。。・゜
public class Solver
{
    static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        var a = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
 
        var dp1 = new int[n + 1, 3 * n + 1];
        var dp2 = new int[n + 1, 3 * n + 1];
        for (int i = 0; i < 3 * n; i++)
        {
            for (int j = 0; j <= n; j++)
            {
                dp1[j, i + 1] = Math.Max(dp1[j, i + 1], dp1[j, i]);
                dp2[j, i + 1] = Math.Max(dp2[j, i + 1], dp2[j, i]);
                if (j < n && i < 3 * n - 1)
                {
                    dp1[j + 1, i + 2] = Math.Max(dp1[j + 1, i + 2], dp1[j, i] + a[i]);
                    dp2[j + 1, i + 2] = Math.Max(dp2[j + 1, i + 2], dp2[j, i] + a[i + 1]);
                }
            }
        }
 
        Console.WriteLine(Math.Max(dp1[n, 3 * n], dp2[n, 3 * n]));
    }
}

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