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: [108.822, 139.139, 130.938, 100.996, 155.361, 8.752, 221.639, -12.877]
Example Output: 106.596

Example Input: [-95.427, -98.447]
Example Output: -96.937

Example Input: [111.553, 152.793, -88.779, 161.076, 75.955, 155.371]
Example Output:
94.662