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: [-89.318, 247.959, 25.441, -92.763, 172.246, -57.286, 181.58]
Example Output: 55.408

Example Input: [24.119, 239.006, 239.873, 236.27, 134.34]
Example Output: 174.722

Example Input: [238.489, 85.764, 219.917, 10.605, -15.771, -69.744, 183.494, -14.646, -14.628, 17.812]
Example Output:
64.129