using System;
using System.Linq;
namespace Yuki
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[] v = Console.ReadLine().Split().Select(z => int.Parse(z)).ToArray();

            int ma = 0;
            int mb = 0;

            for (int i = 0; i < n; i++)
            {
                int a = ma;
                int b = mb;

                if (mb + v[i] > a)
                {
                    ma = mb + v[i];
                }

                if (a > b)
                {
                    mb = a;
                }
            }
            int ans = ma > mb ? ma : mb;

            Console.WriteLine(ans);
        }
    }
}