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: [-53.388, 31.309, 19.079, -16.926, 242.421, 210.599]
Example Output: 72.182

Example Input: [203.498, -79.59, -73.767, -65.942, -8.693]
Example Output: -4.899

Example Input: [135.21, 119.426, 244.466]
Example Output:
166.367