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: [-7.775, 55.997, 216.046]
Example Output: 88.089

Example Input: [14.166, 216.734, -23.073, 209.811, 203.336, 91.659, 142.602, 1.151, -39.869, -54.838]
Example Output: 76.168

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