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: [11.642, -39.595, 23.351, 168.447, 244.85, 108.958, 80.422, -14.774, 138.977]
Example Output: 80.253

Example Input: [-72.554, 9.809, 27.09, 190.698]
Example Output: 38.761

Example Input: [-71.166, 1.639, 40.61, 149.428]
Example Output:
30.128