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: [-17.141, 203.132, -6.872, 155.222, -99.642]
Example Output: 46.94

Example Input: [206.606, -76.103, -16.863, 44.126, 4.019, 15.088]
Example Output: 29.479

Example Input: [34.678, 109.562]
Example Output:
72.12