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: [28.703, 26.223, 100.033, -80.326, -33.283, 241.038, 159.239, -82.352, -90.916]

29.818