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: [1.222, 33.339, 163.969]
Example Output: 66.177

Example Input: [-46.998, -31.307, 129.178, 96.471]
Example Output:
36.836