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: [179.929, 180.162, -63.896, -56.366, 233.638]
Example Output: 94.693

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

Example Input: [20.085, -17.507, -44.329, 41.319]
Example Output:
-0.108