using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Globalization;
using static System.Console;
using Pair = System.Collections.Generic.KeyValuePair<int, int>;

class Program
{
    static void Main()
    {
        var sw = new StreamWriter(OpenStandardOutput()) { AutoFlush = false };
        SetOut(sw);
        new Program().solve();
        Out.Flush();
    }
    Scanner cin = new Scanner();
    readonly int[] dd = { 0, 1, 0, -1, 0 };
    readonly int mod = 1000000007;
    readonly string alfa = "abcdefghijklmnopqrstuvwxyz";

    int n;
    long low, high;
    bool flag;
    void solve()
    {
        n = cin.nextint;
        low = 1; high = (long)Math.Pow(10, 18);
        flag = true;

        var b = new long[n + 1];
        for (int i = 1; i <= n; i++)
        {
            b[i] = cin.nextlong;
            long max = high, min = low;
            if(i % 2 == 1)
            {
                high = b[i] - min;
                low = Math.Max(1, b[i] - max);
            }
            else
            {
                high = max - b[i];
                low = Math.Max(1, min - b[i]);
            }
            if(low > high)
            {
                flag = false;
                break;
            }
        }

        if(flag)
        {
            var a = new long[n + 2];
            a[n + 1] = low;
            for (int i = n; i > 0; i--)
            {
                if(i % 2 == 1)
                {
                    a[i] = b[i] - a[i + 1];
                }
                else
                {
                    a[i] = b[i] + a[i + 1];
                }
            }
            WriteLine(n + 1);
            for (int i = 1; i <= n + 1; i++)
            {
                WriteLine(a[i]);
            }
        }
        else
        {
            WriteLine(-1);
        }
    }

}

class Scanner
{
    string[] s; int i;
    char[] cs = new char[] { ' ' };
    public Scanner() { s = new string[0]; i = 0; }
    public string[] scan { get { return ReadLine().Split(); } }
    public int[] scanint { get { return Array.ConvertAll(scan, int.Parse); } }
    public long[] scanlong { get { return Array.ConvertAll(scan, long.Parse); } }
    public double[] scandouble { get { return Array.ConvertAll(scan, double.Parse); } }
    public string next
    {
        get
        {
            if (i < s.Length) return s[i++];
            string st = ReadLine();
            while (st == "") st = ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            i = 0;
            return next;
        }
    }
    public int nextint { get { return int.Parse(next); } }
    public long nextlong { get { return long.Parse(next); } }
    public double nextdouble { get { return double.Parse(next); } }
}