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: [-42.956, 89.597, -60.477, 101.972, 77.479]
Example Output: 33.123

Example Input: [96.706, 239.918, 73.299, 68.184, 233.512, -76.407]
Example Output: 105.869

Example Input: [204.196, 129.11, 102.851, 204.533, 143.912, 214.911, 89.351, 42.705, 123.403]
Example Output:
139.441