Definition: 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.
Input: [-0.223, -81.443, 108.234, 35.865, -90.363, 30.802, -66.19, 245.018, 3.767]

20.607