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: [229.461, -89.251, 170.954]
Example Output: 103.721

Example Input: [-16.899, 157.634, -93.111]
Example Output:
15.875