input: 
  def mean_median(arr):
      """
      Calculate the mean and median of a given list of numbers.
      
      >>> mean_median([10, 15, 20, 25, 30, 35])
      (22.5, 22.5)
      >>> mean_median([1, 2, 3, 4, 5])
      (3.0, 3)
      """
      arr_sum = 0
      for i in range(len(arr)):
          arr_sum += arr[i]
      
      mean = arr_sum / len(arr)
      
      arr = sorted(arr)
      if len(arr) % 2 != 0:
          median = arr[len(arr) // 2]
      else:
          median = (arr[len(arr) // 2] + arr[len(arr) // 2 - 1]) / 2
      
      return mean, median
  
  mean, median = mean_median([10, 15, 20, 25, 30, 35])
  print("Mean =", mean)
  print("Median =", median)
  
output:     arr_sum = 0
      for i in range(len(arr)):
          arr_sum += arr[i]
      
      mean = arr_sum / len(arr)
      
      arr = sorted(arr)
      if len(arr) % 2 != 0:
          median = arr[len(arr) // 2]
      else:
          median = (arr[len(arr) // 2] + arr[len(arr) // 2 - 1]) / 2
      
      return mean, median