static DoublyLinkedList<Worker> Merge(DoublyLinkedList<Worker> array, int lowIndex, int middleIndex, int highIndex)
        {
            int left = lowIndex;
            int right = middleIndex+1;
            DoublyLinkedList<Worker> tempArray = new DoublyLinkedList<Worker>();
            int index = 1;

            while ((left <= middleIndex) && (right <= highIndex))
            {
                if ( array.Get(left).Data.Surname.CompareTo(array.Get(right).Data.Surname) < 0 )
                {
                    tempArray.Insert(array.Get(left).Data, index);
                    left++;
                }
                else
                {
                    tempArray.Insert(array.Get(right).Data, index);
                    right++;
                }
                index++;
            }

            for (int i = left; i <= middleIndex; i++)
            {
                tempArray.Insert(array.Get(i).Data,index);
                index++;
            }
            for (int i = right; i <= highIndex; i++)
            {
                tempArray.Insert(array.Get(i).Data, index);
                index++;
            }

            for(int i = 1; i <= tempArray.Count; i++)
            {
                array.Insert(tempArray.Get(i).Data, lowIndex-1 + i);
            }
            return array;
        }

static DoublyLinkedList<Worker> MergeSort(DoublyLinkedList<Worker> workers, int lowIndex, int highIndex)
{
  if(lowIndex < highIndex)
       {
         int middleIndex = (lowIndex + highIndex) / 2;
         workers = MergeSort(workers, lowIndex, middleIndex);
         workers = MergeSort(workers, middleIndex + 1, highIndex);
         workers = Merge(workers, lowIndex, middleIndex, highIndex);
        }
  return workers;
}