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: [126.136, -23.429, -25.125, -32.203, 36.405, 44.406, 147.828, -97.708, -69.793, 235.046]
Example Output: 34.156

Example Input: [-3.857, -93.605, 43.857, -73.731, 84.094, -24.492, -41.811, 115.552, 231.429, 130.678]
Example Output: 36.811

Example Input: [-89.81, -83.253, 140.015, 105.792, -6.112]
Example Output:
13.326