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: [-40.509, 201.39]
Example Output: 80.44

Example Input: [248.385, -40.468, -97.132]
Example Output: 36.928

Example Input: [225.022, 61.063, 163.442]
Example Output:
149.842