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

namespace ConsoleApp1
{
    class Program
    {
        static IEnumerable<IEnumerable<int>> SelectNElements(int[] arr, int n)
        {
            IEnumerable<IEnumerable<int>> result = arr.Select(x => new List<int>() { x });
            for (int i = 1; i < n; i++)
                result = result.SelectMany(x => arr.Where(y => y > x.Max()), (x, y) => x.Concat(new int[] { y }));
            return result;
        }
        static void Main(string[] args)
        {
            int[] arr = { 1, 2, 3, 4 };
            for (int i = 1; i <= arr.Length; i++)
            {
                var result = SelectNElements(arr, i);
                foreach (var item in result)
                {
                    foreach (int x in item)
                        Console.Write(x + " ");
                    Console.WriteLine();
                }
            }
        }
    }
}