using System;
using System.Linq;

internal class Program
{
    public static void Main(string[] args)
    {
        var d = int.Parse(Console.ReadLine());
        var nums = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
        for (int i = d; i >= 3; i--)
        {
            nums[i - 2] += nums[i];
            nums[i] = 0;
        }
        int modD = 0;
        for (int i = Math.Min(2, d); i >= 0; i--)
        {
            if (nums[i] != 0)
            {
                modD = i;
                break;
            }
        }
        Console.WriteLine(modD);
        for (int i = 0; i < modD; i++)
        {
            Console.Write(nums[i] + " ");
        }
        Console.WriteLine(nums[modD]);
    }
}