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: [127.522, 232.86, 46.593]
Example Output: 135.658

Example Input: [-19.769, 147.929, -36.133, 201.287, 28.528, -6.089, 122.533, 127.892, -36.662]
Example Output: 58.835

Example Input: [-66.648, 71.798, -71.769, -6.856]
Example Output:
-18.369