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: [226.383, 37.978, 174.444, 117.212]
Example Output: 139.004

Example Input: [-36.318, 176.066, 36.435, 132.732, -15.887, -24.851, 169.963, -98.796, 38.818]
Example Output: 42.018

Example Input: [43.897, 142.481, 57.194, 233.621]
Example Output:
119.298