using System;
using System.Linq;

namespace No451
{
    class Program
    {
        static void Main(string[] args)
        {
            var n = Convert.ToInt32(Console.ReadLine());
            var input = ReadLines(n);
            var evens = input.Where((x, i) => i % 2 == 0).ToArray();
            var min = evens.Min();
            if (min < 2) { Console.WriteLine(-1); return; }
            var minidx = getIndex(evens, min) * 2;
            var output = new long[n + 1];
            output[minidx] = 1;
            for (var i = minidx - 1; i > -1; i--)
            {
                if (i % 2 == 1)
                {
                    output[i] = input[i] + output[i + 1];
                }
                else
                {
                    output[i] = input[i] - output[i + 1];
                }
            }
            for (var i = minidx; i < n; i++)
            {
                if (i % 2 == 1)
                {
                    output[i+1] = output[i] - input[i];
                }
                else
                {
                    output[i+1] = input[i] - output[i];
                }
            }
            if (output.Min() < 1)
            {
                Console.WriteLine(-1);
                return;
            }

            Console.WriteLine(n + 1);
            foreach(var num in output)
            {
                Console.WriteLine(num);
            }
        }

        static long[] ReadLines(int times)
        {
            var ret = new long[times];
            for (var i = 0; i < times; i++)
            {
                ret[i] = Convert.ToInt64(Console.ReadLine());
            }
            return ret;
        }

        static int getIndex(long[] array, long value)
        {
            for (var i = 0; i < array.Length; i++)
            {
                if(array[i] == value)
                {
                    return i;
                }
            }
            return -1;
        }
    }
}