using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace szigetek
{
    internal class Program
    {
        static void Main(string[] args)
        {
            string sor = Console.ReadLine();
            int db = int.Parse(sor);
            sor = Console.ReadLine();
            string[] tsor = sor.Split(' ');
            List<int> lista = new List<int>();
            List<int> reslist = new List<int>();
            for(int i = 0; i < tsor.Length; i++)
            {
                lista.Add(int.Parse(tsor[i]));
            }
            int j = 2;
            reslist.Add(lista[0]);
            reslist.Add(lista[1] + lista[0]);
            while(j < lista.Count)
            {
                if (reslist[j-1] < reslist[j - 2])
                {
                    reslist.Add(lista[j] + reslist[j-1]);
                }
                else
                {
                    reslist.Add(lista[j] + reslist[j - 2]);
                }
                j++;
            }
            Console.WriteLine(reslist[reslist.Count()-1]);
        }
    }
}