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: [128.328, 20.497, 96.178, 237.663, 80.568, 109.722]
Example Output: 112.159

Example Input: [-57.838, -63.616, 49.646, -45.262, 73.1, -82.399, 47.168]
Example Output: -11.314

Example Input: [-80.23, -64.886, 14.991, -75.9]
Example Output:
-51.506