using System;

public class Program

{

    public static void Main()

    {

        double[] arr = { 76, 89, 23, 1, 55, 78, 99, 12, 65, 100 };

            int n = 10, i;

            double sum = 0;

            Console.WriteLine("Merge Sort");

            Console.Write("Initial array is: ");

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

            {

                Console.Write(arr[i] + " ");

            }

            MergeSort(arr, 0, arr.Length - 1);

            Console.Write("Sorted Array is: ");

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

            {

                Console.Write(arr[i] + " ");

            }

​

            foreach (var el in arr)

            {

                if (el<0)

                {

                    sum += el;

                }

            }

            Console.WriteLine("{0}",sum);

     }

​

        static void MergeSort(double[] arr, double start, double end)

        {

            if (start >= end) return;

            double middle = (start + end) / 2;

            MergeSort(arr, start, middle);

            MergeSort(arr, middle + 1, end);

            CompareAndSort(arr, start, middle, end);

        }

        static void CompareAndSort( double[] arr, double start, double middle, double end)

        {

            double[] sortedArr = new double[arr.Length];

            int left_tmp = start, left_arr = start, middle_arr = middle + 1;

            while (left_arr <= middle && middle_arr <= end)

            {

                if (arr[left_arr] > arr[middle_arr])

                {

                    sortedArr[left_tmp] = arr[middle_arr];

                    left_tmp++;

                    middle_arr++;

                }           

                else

                {

                    sortedArr[left_tmp] = arr[left_arr];

                    left_tmp++;

                    left_arr++;

                }

            }

            while (left_arr <= middle)

            {

                sortedArr[left_tmp] = arr[left_arr];

                left_tmp++;

                left_arr++;

            }

            while (middle_arr <= end)

            {

                sortedArr[left_tmp] = arr[middle_arr];

                left_tmp++;

                middle_arr++;

            }

            for (int i = start; i <= end; i++)

            {

                arr[i] = sortedArr[i];

            }

        }   

}

​

​