using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var list = new List<int>{8, 7, 6, 4, 43, 23, 435, 76, 7, 7877, 5, 421, 2};

        var results = MergeSplit(new Queue<int>(list));

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

    }

​

    private static Queue<int> Merge(Queue<int> left, Queue<int> right)

    {

        var result = new Queue<int>();

        while (left.Count > 0 && right.Count > 0)

            result.Enqueue(left.Peek() > right.Peek() ? right.Dequeue() : left.Dequeue());

        foreach (var item in left)

            result.Enqueue(item);

        foreach (var item in right)

            result.Enqueue(item);

        return result;

    }

​

    private static Queue<int> MergeSplit(Queue<int> list)

    {

        var n = list.Count;

        if (n <= 1) return list;

        var left = new Queue<int>();

        var right = new Queue<int>();

        for (var i = 0; i < n; i++)

            if (i < n / 2)

                left.Enqueue(list.Dequeue());

            else

                right.Enqueue(list.Dequeue());

        left = MergeSplit(left);

        right = MergeSplit(right);

        return Merge(left, right);

    }

}