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: [207.804, 175.122, 13.63, 217.625, -98.484]
Example Output: 103.139

Example Input: [30.224, 63.76, 96.876, 149.052, -38.974, 48.35, 133.493, 142.787, 10.958]
Example Output: 70.725

Example Input: [230.118, 62.129]
Example Output:
146.124