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

namespace Kerekpartura
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[] d = Console.ReadLine().Split().Select(int.Parse).ToArray();
            int[] val = new int[n];
            val[0] = d[0];
            val[1] = d[1] + d[0];
            for (int i = 2; i < n; i++)
            {
                val[i] = Math.Min(val[i - 1], val[i - 2]) + d[i];
            }
            Console.WriteLine(val[n - 1]);
            Console.ReadLine();
        }
    }
}