input: Write a python function to find the median of a list of numbers.
  assert getMedian([1, 3, 3, 6, 7, 8, 9]) == 6
  assert getMedian([1, 2, 3, 4, 5, 6, 8, 9]) == 4.5
  assert getMedian([1, 2, 3]) == 2
output: def getMedian(numbers):
      numbers.sort()
      n = len(numbers)
      if n % 2 == 1:
          return numbers[n // 2]
      else:
          mid1, mid2 = n // 2 - 1, n // 2
          return (numbers[mid1] + numbers[mid2]) / 2