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: [-79.521, 169.962, 120.036, -71.612, -53.261, -90.734, -35.559, 140.419, 25.016]
Example Output: 13.861

Example Input: [-11.211, 9.955, 208.942, 124.097, 118.282, 65.001]
Example Output: 85.844

Example Input: [84.166, 81.558, -89.721]
Example Output:
25.334