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: [192.74, 78.623, -5.937, 144.535]
Example Output: 102.49

Example Input: [-40.016, 117.495]
Example Output: 38.74

Example Input: [141.896, 234.549, -9.124, -77.691]
Example Output:
72.408