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: [142.225, 243.809, -41.935, 96.795, -99.067, 222.292, 113.486, 143.726]
Example Output: 102.666

Example Input: [-59.526, 55.871, 118.248, 197.073]
Example Output: 77.916

Example Input: [137.571, 151.937, 187.469, 238.253]
Example Output:
178.808