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: [5.703, -17.365, 21.827, 38.836, 5.17, -15.533]
Example Output: 6.44

Example Input: [16.256, 155.71, 43.059, -64.109, -42.445, 78.725, -12.941, 47.497]
Example Output: 27.719

Example Input: [-71.709, 174.193, -84.665]
Example Output:
5.94