StackOverflow

Experiment

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

namespace AppendArrays
{
    class Program
    {
        static void Main(string[] args)
        {
            List<string> numbersAsStrings = Console.ReadLine()
                                 .Split('|')
                                 .Reverse()
                                 .ToList();
            List<int> numbers = new List<int>();
            foreach (var str in numbersAsStrings)
            {
                numbers.AddRange(str.Split(new[] { " " }, StringSplitOptions.RemoveEmptyEntries)
                                    .Select(int.Parse)
                                    .ToList()
                                     );
                // Zapiswam stoinostite ot stariq List w nov List
                // Smeneni sa oshte gore s .Reverse
            }
            Console.WriteLine(string.Join(" ", numbers));

        }
    }
}