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: [-19.13, 98.86, 158.686, 230.23]
Example Output: 117.161

Example Input: [213.2, 159.287, 214.859, 189.464, 185.706, -85.847, 215.647, 8.545]
Example Output: 137.608

Example Input: [-13.097, 181.545, -77.036, 48.277, -4.675, 81.544]
Example Output:
36.093