using System;

​

public class Program

{

    public static void Main()

    {

        var A = new int[]{1, 2, 3, 0, 0, 0};

        int m = 3;

        var B = new int[]{2, 5, 6};

        int n = 3;

        PrintArray(A);

        Console.WriteLine("\n");

        PrintArray(B);

        var C = Merge(A, m, B, n);

        Console.WriteLine("\n");

        PrintArray(C);

    }

​

    public static int[] Merge(int[] A, int m, int[] B, int n)

    {

        int aindex = m - 1;

        int bindex = n - 1;

        while (aindex >= 0 || bindex >= 0)

        {

            int avalue = aindex >= 0 ? A[aindex] : int.MinValue;

            int bvalue = bindex >= 0 ? B[bindex] : int.MinValue;

            if (avalue > bvalue)

            {

                A[aindex + bindex + 1] = avalue;

                aindex--;

            }

            else

            {

                A[aindex + bindex + 1] = bvalue;

                bindex--;

            }

        }

​

        return A;

    }

​

    public static void PrintArray(int[] input)

    {

        Console.Write("[");

        foreach (int item in input)

        {

            Console.Write($"{item}");

            Console.Write(",");

        }

​

        Console.Write("]");

    }

}