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: [-66.271, 56.586, -21.072, 136.915, 54.951, 112.054]
Example Output: 45.527

Example Input: [162.26, 79.268]
Example Output: 120.764

Example Input: [-59.098, -22.489]
Example Output:
-40.794