Assertions

Lab Python Intermediate 20 points

Write average(nums) that starts with assert nums, "empty list". Read a line (possibly just - meaning empty) and print the average with 2 decimals or AssertionError: empty list.

Input

One line of integers, or -.

Output

One line.

Example

Input

1 2 3 4

Output

2.50

Sample input available Sample output available

Editor

Python

Hints

assert condition, message raises AssertionError when the condition is false.

Solution explanation

Assertions check assumptions during development. Don't use them to validate user input in production - they can be disabled with python -O.

Show solution

def average(nums):
    assert nums, "empty list"
    return sum(nums) / len(nums)


text = input()
nums = [] if text == "-" else list(map(int, text.split()))
try:
    print(f"{average(nums):.2f}")
except AssertionError as err:
    print(f"AssertionError: {err}")

Output

Answer