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: [-66.735, 23.822, -34.5, 118.327, 242.333]
Example Output: 56.649

Example Input: [66.666, -70.196, -39.152]
Example Output: -14.227

Example Input: [-41.714, 218.588, 49.769, 142.519, 179.776, -99.226, 224.69, 191.642]
Example Output:
108.256