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: [238.315, 168.986, -67.694]
Example Output: 113.202

Example Input: [159.381, -84.046]
Example Output: 37.668

Example Input: [30.947, 240.077, 183.058, -90.888, -96.048, 95.125]
Example Output:
60.378