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: [71.91, 41.513]
Example Output: 56.712

Example Input: [178.694, -18.914, 30.093, -42.535, 10.965, 20.697]
Example Output:
29.833