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: [-66.387, 135.639, 182.921, 175.573, 105.67, -29.751, 156.67, 83.119, 19.538]
Example Output: 84.777

Example Input: [84.142, -99.804]
Example Output: -7.831

Example Input: [203.519, -11.741, 85.426, -45.034, 80.174]
Example Output:
62.469