#!/usr/bin/python
"""This program takes lines of 
integers on standard input and returns
the average of each line of integers."""

# Import the sys module for access to stdin and stdout.
import sys

def average(numbers):
	"""averages takes a list of integers as its
argument and returns their average as a float."""

	total = 0
	
	for number in numbers:
		total += int(number)

	return total/float(len(numbers))


for line in sys.stdin:

	# Get the average of the integers
	#  Since we get each line of stdin as
	#  a string, we use split() to give us
	#  a list of the individual words (which
	#  should all be integers).
	avg = average(line.split())

	# Format the output:
	#  Express our average to 2 decimal places, and
	#  also include the original line (for checking)
	output = "%.2f: %s" % (avg, line)

	# Write it to stdout
	sys.stdout.write(output)