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: [65.727, 216.759, 101.145, 91.028]
Example Output: 118.665

Example Input: [183.332, -51.581, -15.684, 140.965, 37.376, 37.734, 71.356]
Example Output: 57.643

Example Input: [195.575, 136.671, 133.954, 130.232, 72.902, 143.962, 228.458, 69.239, 137.6]
Example Output:
138.733