def merge_sort(arr):

    if len(arr) > 1:
        mid = len(arr) // 2
        left = arr[:mid]
        right = arr[mid:]
        merge_sort(left)
        merge_sort(right)


        left_pointer, right_pointer, arr_pointer = 0, 0, 0

        while left_pointer < len(left) and right_pointer < len(right):

            if left[left_pointer] < right[right_pointer]:
                arr[arr_pointer] = left[left_pointer]
                left_pointer += 1
                arr_pointer += 1
            else:
                arr[arr_pointer] = right[right_pointer]
                right_pointer += 1
                arr_pointer += 1
                swaps += 1

            # handling the rest items

        while left_pointer < len(left):
            arr[arr_pointer] = left[left_pointer]
            left_pointer += 1
            arr_pointer += 1

        while right_pointer < len(right):
            arr[arr_pointer] = right[right_pointer]
            right_pointer += 1
            arr_pointer += 1


    return swaps

print (merge_sort([3,1,2,4,6,1]))