using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;

class Magatro
{

    static void Main()
    {
        int D = int.Parse(Console.ReadLine());
        int[] a = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
        if (D == 0)
        {
            Console.WriteLine("0\n0");
        }
        if (D < 3)
        {
            Console.WriteLine(D);
            for(int i = 0; i < D; i++)
            {
                Console.Write(a[i]+" ");

            }
            Console.Write(a[D] + "\n");
        }
        for(int i = D; i >=3; i--)
        {
            a[i - 2] += a[i];
            a[i] = 0;
        }
        bool aa = false;
        string ans = "";
        int DD=0;
        int aaa = a[0];
        int bbb = a[1];
        int ccc = a[2];
        if (ccc == 0)
        {
            if (bbb == 0)
            {
                Console.WriteLine(0);
                Console.WriteLine(aaa);
            }
            else
            {
                Console.WriteLine(1);
                Console.WriteLine("{0} {1}", aaa, bbb);
            }
        }
        else
        {
            Console.WriteLine(2);
            Console.WriteLine("{0} {1} {2}", aaa, bbb, ccc);
        }
    }
}