In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.

Example Input: [100.422, 199.731, 138.971, 95.515, 9.517]
Example Output: 108.831

Example Input: [215.854, -43.532, 51.416]
Example Output: 74.579

Example Input: [-0.23, 117.845, -87.306, -51.963, 148.074]
Example Output:
25.284