using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var input = new List<int[]> 

        {

            new int[] {1,2,4,5,6},

            new int[] {3,4,5,8,9},

            new int[] {1,2,3,10,12},

            new int[] {2,4,6,9,11},

        };

        var result = MergeAll(input, 0, input.Count);

        foreach(var index in result)

            Console.Write(index + ", ");

    }

    public static int[] MergeAll(List<int[]> input, int start, int end)

    {

        if(start == input.Count)

            return new int[0];

        if(start == end)

            return input[start];

        if(start - end == 1)

            return MergeArrays(input[start], input[end]);

        int mid = (int)Math.Floor((double)(start+end)/2);

        var upper = MergeAll(input, mid + 1, end);

        var lower = MergeAll(input, start, mid);

        return MergeArrays(upper, lower);

    }

    public static int[] MergeArrays(int[] arr1, int[] arr2)

    {

        int n = arr1.Length;

        int m = arr2.Length;

        int[] mergedArray = new int[n + m];

​

        int i = 0, j = 0, k = 0;

        for(int i = 0, j = 0, k = 0; k < m+ n; k ++)

        {

            if(i >

        }

        // Compare elements from both arrays and merge into mergedArray

        while (i < n && j < m)

        {

            if (arr1[i] <= arr2[j])

            {

                mergedArray[k] = arr1[i];

                i++;

            }

            else

            {

                mergedArray[k] = arr2[j];

                j++;

            }

            k++;

        }

​

        // Add remaining elements from arr1, if any

        while (i < n)

        {

            mergedArray[k] = arr1[i];

            i++;

            k++;

        }

​

        // Add remaining elements from arr2, if any

        while (j < m)

        {

            mergedArray[k] = arr2[j];

            j++;

            k++;

        }

​

        return mergedArray;

    }

}