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: [70.553, 193.054, 166.173, 115.812]
Example Output: 136.398

Example Input: [126.198, -70.303]
Example Output: 27.947

Example Input: [146.762, 149.536, 42.391, -64.743]
Example Output:
68.486