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: [183.332, -51.581, -15.684, 140.965, 37.376, 37.734, 71.356]
Example Output: 57.643

Example Input: [-47.309, -46.076, 191.14, -6.032, 4.858]
Example Output: 19.316

Example Input: [13.828, 155.859, 207.974, -44.32, 120.722, 115.533, -23.042, 41.755, 76.642]
Example Output:
73.883