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: [49.035, -81.115, 27.419]
Example Output: -1.554

Example Input: [120.236, 116.311, -13.268]
Example Output: 74.426

Example Input: [-20.764, 159.3, 157.026, 26.303, 61.888, 148.158, -3.324]
Example Output:
75.512