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: [-56.201, -77.67, -75.53, -51.92, 146.416, 141.525]
Example Output: 4.437

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

Example Input: [-0.52, 249.164, 11.78, 81.615]
Example Output:
85.51