using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp10
{
    class Program
    {
        static void Main()
        {
            int[] numbers = { 1, 2, 3, 4 };
            int[] numbers1 = { 5, 6, 7, 8 };
            int[] dblNumbers = new int[numbers.Length * 2];

            int[] result = numbers.Concat(numbers1).ToArray();

            for (int i = 0; i < result.Length; i++)
            {
                for (int j = 0; j < numbers1.Length; j++)
                {
                    dblNumbers[i] = numbers[i];
                }
                for (int k = 0; k < numbers.Length; k++)
                {
                    dblNumbers[i] = numbers[i];
                }
            }


            Console.WriteLine(string.Join(", ", dblNumbers));

        }
    }
}