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: [-40.016, 117.495]
Example Output: 38.74

Example Input: [14.587, 49.21, -21.274, -54.714, 243.935, 218.436]
Example Output: 75.03

Example Input: [-42.36, 50.276]
Example Output:
3.958