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: [-2.772, 225.483, 211.749, 45.779, -82.623, 229.799, 107.783, 64.653]
Example Output: 99.981

Example Input: [128.472, 149.361, 71.023, -96.651]
Example Output: 63.051

Example Input: [-86.961, -47.951, 143.862, 44.642, 144.616, 187.7, 183.32]
Example Output:
81.318