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: [49.035, -81.115, 27.419]
Example Output: -1.554

Example Input: [-96.502, 12.006]
Example Output: -42.248

Example Input: [120.682, 53.847]
Example Output:
87.264