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: [-7.892, -43.609, 46.236, -78.213, -76.066]
Example Output: -31.909

Example Input: [2.81, 52.99, 55.279, 75.682, 73.835, 148.077, -54.162, 112.112]
Example Output: 58.328

Example Input: [243.316, -0.7, 185.359, -99.793]
Example Output:
82.046