#
#  Compute the median of a collection of values entered by the user.
#

#
#  Read numbers from the user until a blank line is entered.
# 
#  Parameters: (None)
#
#  Returns: A list of all the values entered by the user as floating point
#           numbers.
#
def readNumbers():
  # Read the first value from the user
  line = input("Enter a number: ")
  # Create an empty list to store the values
  data = []

  # While the user has not entered a blank line
  while line != "":
    # Convert the entered value to a floating point number
    num = float(line)

    # Add the number to the list of values
    data.append(num)

    # Read the next line from the user
    line = input("Enter a number: ")

  # Return the list of values read from the user
  return data


#
#  Compute the median of a collection of values.
#
#  Parameters:
#    data: A non-empty list of numbers.
#
#  Returns: The median of the numbers stored in data.
#
def median(data):
  #
  #  Sort the values.
  #
  data.sort()

  #
  #  Compute the median.
  #
  if len(data) % 2 == 0:
    # An even number of values were entered so the median is the average
    # of the two middle values
    median = (data[len(data) // 2] + data[len(data) // 2 - 1]) / 2
  else:
    # An odd number of values was entered so the median is the middle value
    median = data[len(data) // 2]

  #
  #  Return the median.
  #
  return median

#
#  Compute the median of a collection of values entered by the user
#
def main():
  values = readNumbers()
  if len(values) == 0:
    # No values were entered
    print("The median cannot be computed because no values were entered.")
  else:
    # One or more values were entered so the median can be computed and 
    # reported.
    m = median(values)
    print("The median value is", m)

main()