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: [219.769, -36.26, 3.121, -22.5, 124.372]
Example Output: 57.7

Example Input: [-8.87, 232.908, 141.714, -47.559, 161.192, 203.441]
Example Output: 113.804

Example Input: [153.141, -71.109, 231.067, -37.855]
Example Output:
68.811