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: [-94.827, -4.806, 33.138, 11.562, -68.261]
Example Output: -24.639

Example Input: [218.807, 72.849, 7.838, 124.81, 45.929, 239.888]
Example Output: 118.354

Example Input: [223.346, -17.239, -26.413, -29.137, -61.666, 210.691, 97.973, -51.365, 99.191]
Example Output:
49.487